19 symbolic expressions and functions. |
27 symbolic expressions and functions. |
20 |
28 |
21 .. #[Nishanth]: The formatting is all messed up |
29 .. #[Nishanth]: The formatting is all messed up |
22 First fix the formatting and compile the rst |
30 First fix the formatting and compile the rst |
23 The I shall review |
31 The I shall review |
24 |
32 .. #[Madhu: Please make the above items full english sentences, not |
25 Using sage we can perform mathematical operations on symbols . |
33 the slides like points. The person recording should be able to |
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34 read your script as is. It can read something like "we will learn |
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35 how to define symbolic expressions in Sage, using built-in ..."] |
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36 |
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37 Using sage we can perform mathematical operations on symbols. |
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38 |
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39 .. #[Madhu: Same mistake with period symbols! Please get the |
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40 punctuation right. Also you may have to rephrase the above |
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41 sentence as "We can use Sage to perform sybmolic mathematical |
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42 operations" or such] |
26 |
43 |
27 On the sage notebook type:: |
44 On the sage notebook type:: |
28 |
45 |
29 sin(y) |
46 sin(y) |
30 |
47 |
31 It raises a name error saying that y is not defined . But in sage we |
48 It raises a name error saying that y is not defined. But in sage we |
32 can declare y as a symbol using var function. :: |
49 can declare y as a symbol using var function. |
33 |
50 |
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51 .. #[Madhu: But is not required] |
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52 :: |
34 var('y') |
53 var('y') |
35 |
54 |
36 Now if you type:: |
55 Now if you type:: |
37 |
56 |
38 sin(y) |
57 sin(y) |
39 |
58 |
40 sage simply returns the expression . |
59 sage simply returns the expression . |
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60 |
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61 .. #[Madhu: Why is this line indented? Also full stop. When will you |
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62 learn? Yes we can correct you. But corrections are for you to |
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63 learn. If you don't learn from your mistakes, I don't know what |
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64 to say] |
41 |
65 |
42 thus now sage treats sin(y) as a symbolic expression . You can use |
66 thus now sage treats sin(y) as a symbolic expression . You can use |
43 this to do a lot of symbolic maths using sage's built-in constants and |
67 this to do a lot of symbolic maths using sage's built-in constants and |
44 expressions . |
68 expressions . |
45 |
69 |
46 Try out :: |
70 .. #[Madhu: "Thus now"? It sounds like Dus and Nou, i.e 10 and 9 in |
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71 Hindi! Full stop again. "a lot" doesn't mean anything until you |
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72 quantify it or give examples.] |
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73 |
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74 Try out |
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75 |
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76 .. #[Madhu: "So let us try" sounds better] |
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77 :: |
47 |
78 |
48 var('x,alpha,y,beta') x^2/alpha^2+y^2/beta^2 |
79 var('x,alpha,y,beta') x^2/alpha^2+y^2/beta^2 |
49 |
80 |
50 Similarly , we can define many algebraic and trigonometric expressions |
81 Similarly , we can define many algebraic and trigonometric expressions |
51 using sage . |
82 using sage . |
52 |
83 |
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84 .. #[Madhu: comma again. Show some more examples?] |
53 |
85 |
54 |
86 |
55 Sage also provides a few built-in constants which are commonly used in |
87 Sage also provides a few built-in constants which are commonly used in |
56 mathematics . |
88 mathematics . |
57 |
89 |
58 example : pi,e,oo , Function n gives the numerical values of all these |
90 example : pi,e,oo , Function n gives the numerical values of all these |
59 constants. |
91 constants. |
60 |
92 |
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93 .. #[Madhu: This doesn't sound like scripts. How will I read this |
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94 while recording. Also if I were recording I would have read your |
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95 third constant as Oh-Oh i.e. double O. It took me at least 30 |
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96 seconds to figure out it is infinity] |
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97 |
61 For instance:: |
98 For instance:: |
62 |
99 |
63 n(e) |
100 n(e) |
64 |
101 |
65 2.71828182845905 |
102 2.71828182845905 |
66 |
103 |
67 gives numerical value of e. |
104 gives numerical value of e. |
68 |
105 |
69 If you look into the documentation of n by doing :: |
106 If you look into the documentation of n by doing |
70 |
107 |
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108 .. #[Madhu: "documentation of the function "n"?] |
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109 |
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110 :: |
71 n(<Tab> |
111 n(<Tab> |
72 |
112 |
73 You will see what all arguments it can take etc .. It will be very |
113 You will see what all arguments it can take etc .. It will be very |
74 helpful if you look at the documentation of all functions introduced |
114 helpful if you look at the documentation of all functions introduced |
75 |
115 |
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116 .. #[Madhu: What does etc .. mean in a script?] |
76 |
117 |
77 Also we can define the no of digits we wish to use in the numerical |
118 Also we can define the no of digits we wish to use in the numerical |
78 value . For this we have to pass an argument digits. Type:: |
119 value . For this we have to pass an argument digits. Type |
79 |
120 |
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121 .. #[Madhu: "no of digits"? Also "We wish to obtain" than "we wish to |
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122 use"?] |
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123 :: |
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124 |
80 n(pi, digits = 10) |
125 n(pi, digits = 10) |
81 |
126 |
82 Apart from the constants sage also has a lot of builtin functions like |
127 Apart from the constants sage also has a lot of builtin functions like |
83 sin,cos,sinh,cosh,log,factorial,gamma,exp,arcsin,arccos,arctan etc ... |
128 sin,cos,sinh,cosh,log,factorial,gamma,exp,arcsin,arccos,arctan etc ... |
84 lets try some out on the sage notebook. :: |
129 lets try some out on the sage notebook. |
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130 |
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131 .. #[Madhu: Here "a lot" makes sense] |
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132 :: |
85 |
133 |
86 sin(pi/2) |
134 sin(pi/2) |
87 |
135 |
88 arctan(oo) |
136 arctan(oo) |
89 |
137 |
94 an arbitrary function with desired name in the following way.:: |
142 an arbitrary function with desired name in the following way.:: |
95 |
143 |
96 var('x') function(<tab> {{{ Just to show the documentation |
144 var('x') function(<tab> {{{ Just to show the documentation |
97 extend this line }}} function('f',x) |
145 extend this line }}} function('f',x) |
98 |
146 |
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147 .. #[Madhu: What will the person recording show in the documentation |
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148 without a script for it? Please don't assume recorder can cook up |
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149 things while recording. It is impractical] |
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150 |
99 Here f is the name of the function and x is the independent variable . |
151 Here f is the name of the function and x is the independent variable . |
100 Now we can define f(x) to be :: |
152 Now we can define f(x) to be :: |
101 |
153 |
102 f(x) = x/2 + sin(x) |
154 f(x) = x/2 + sin(x) |
103 |
155 |
104 Evaluating this function f for the value x=pi returns pi/2.:: |
156 Evaluating this function f for the value x=pi returns pi/2.:: |
105 |
157 |
106 f(pi) |
158 f(pi) |
107 |
159 |
108 We can also define function that are not continuous but defined |
160 We can also define functions that are not continuous but defined |
109 piecewise. We will be using a function which is a parabola between 0 |
161 piecewise. We will be using a function which is a parabola between 0 |
110 to 1 and a constant from 1 to 2 . type the following as given on the |
162 to 1 and a constant from 1 to 2 . type the following as given on the |
111 screen:: |
163 screen |
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164 |
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165 .. #[Madhu: Instead of "We will be using ..." how about "Let us define |
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166 a function ..."] |
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167 :: |
112 |
168 |
113 |
169 |
114 var('x') h(x)=x^2 g(x)=1 f=Piecewise(<Tab> {{{ Just to show the |
170 var('x') h(x)=x^2 g(x)=1 f=Piecewise(<Tab> {{{ Just to show the |
115 documentation extend this line }}} |
171 documentation extend this line }}} |
116 f=Piecewise([[(0,1),h(x)],[(1,2),g(x)]],x) f |
172 f=Piecewise([[(0,1),h(x)],[(1,2),g(x)]],x) f |
117 |
173 |
118 Checking f at 0.4, 1.4 and 3 :: f(0.4) f(1.4) f(3) |
174 Checking f at 0.4, 1.4 and 3 :: f(0.4) f(1.4) f(3) |
119 |
175 |
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176 .. #[Madhu: Again this doesn't sound like a script] |
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177 |
120 for f(3) it raises a value not defined in domain error . |
178 for f(3) it raises a value not defined in domain error . |
121 |
179 |
122 |
180 |
123 Apart from operations on expressions and functions one can also use |
181 Apart from operations on expressions and functions one can also use |
124 them for series . |
182 them for series . |
125 |
183 |
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184 .. #[Madhu: I am not able to understand this line. "Use them as |
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185 .. series". Use what as series?] |
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186 |
126 We first define a function f(n) in the way discussed above.:: |
187 We first define a function f(n) in the way discussed above.:: |
127 |
188 |
128 var('n') function('f', n) |
189 var('n') function('f', n) |
129 |
190 |
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191 .. #[Madhu: Shouldn't this be on 2 separate lines?] |
130 |
192 |
131 To sum the function for a range of discrete values of n, we use the |
193 To sum the function for a range of discrete values of n, we use the |
132 sage function sum. |
194 sage function sum. |
133 |
195 |
134 For a convergent series , f(n)=1/n^2 we can say :: |
196 For a convergent series , f(n)=1/n^2 we can say :: |
135 |
197 |
136 var('n') function('f', n) |
198 var('n') function('f', n) |
137 |
199 |
138 f(n) = 1/n^2 |
200 f(n) = 1/n^2 |
139 |
201 |
140 sum(f(n), n, 1, oo) |
202 sum(f(n), n, 1, oo) |
141 |
203 |
142 For the famous Madhava series :: var('n') function('f', n) |
204 For the famous Madhava series :: var('n') function('f', n) |
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205 |
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206 .. #[Madhu: What is this? your double colon says it must be code block |
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207 but where is the indentation and other things. How will the |
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208 recorder know about it?] |
143 |
209 |
144 f(n) = (-1)^(n-1)*1/(2*n - 1) |
210 f(n) = (-1)^(n-1)*1/(2*n - 1) |
145 |
211 |
146 This series converges to pi/4. It was used by ancient Indians to |
212 This series converges to pi/4. It was used by ancient Indians to |
147 interpret pi. |
213 interpret pi. |
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214 |
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215 .. #[Madhu: I am losing the context. Please add something to bring |
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216 this thing to the context] |
148 |
217 |
149 For a divergent series, sum would raise a an error 'Sum is |
218 For a divergent series, sum would raise a an error 'Sum is |
150 divergent' :: |
219 divergent' :: |
151 |
220 |
152 var('n') |
221 var('n') |
156 |
225 |
157 |
226 |
158 |
227 |
159 We can perform simple calculus operation using sage |
228 We can perform simple calculus operation using sage |
160 |
229 |
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230 .. #[Madhu: When you switch to irrelevant topics make sure you use |
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231 some connectors in English like "Moving on let us see how to |
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232 perform simple calculus operations using Sage" or something like |
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233 that] |
161 For example lets try an expression first :: |
234 For example lets try an expression first :: |
162 |
235 |
163 diff(x**2+sin(x),x) 2x+cos(x) |
236 diff(x**2+sin(x),x) 2x+cos(x) |
164 |
237 |
165 The diff function differentiates an expression or a function . Its |
238 The diff function differentiates an expression or a function . Its |
166 first argument is expression or function and second argument is the |
239 first argument is expression or function and second argument is the |
167 independent variable . |
240 independent variable . |
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241 |
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242 .. #[Madhu: Full stop, Full stop, Full stop] |
168 |
243 |
169 We have already tried an expression now lets try a function :: |
244 We have already tried an expression now lets try a function :: |
170 |
245 |
171 f=exp(x^2)+arcsin(x) diff(f(x),x) |
246 f=exp(x^2)+arcsin(x) diff(f(x),x) |
172 |
247 |
173 To get a higher order differentiation we need to add an extra argument |
248 To get a higher order differentiation we need to add an extra argument |
174 for order :: |
249 for order :: |
175 |
250 |
176 diff(<tab> diff(f(x),x,3) |
251 diff(<tab> diff(f(x),x,3) |
177 |
252 |
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253 .. #[Madhu: Please try to be more explicit saying third argument] |
178 |
254 |
179 in this case it is 3. |
255 in this case it is 3. |
180 |
256 |
181 |
257 |
182 Just like differentiation of expression you can also integrate them :: |
258 Just like differentiation of expression you can also integrate them :: |
183 |
259 |
184 x = var('x') s = integral(1/(1 + (tan(x))**2),x) s |
260 x = var('x') s = integral(1/(1 + (tan(x))**2),x) s |
185 |
261 |
186 |
262 .. #[Madhu: Two separate lines.] |
187 |
263 |
188 To find factors of an expression use the function factor |
264 To find the factors of an expression use the "factor" function |
189 |
265 |
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266 .. #[Madhu: See the diff] |
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267 |
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268 :: |
190 factor(<tab> y = (x^100 - x^70)*(cos(x)^2 + cos(x)^2*tan(x)^2) f = |
269 factor(<tab> y = (x^100 - x^70)*(cos(x)^2 + cos(x)^2*tan(x)^2) f = |
191 factor(y) |
270 factor(y) |
192 |
271 |
193 One can also simplify complicated expression using sage :: |
272 One can also simplify complicated expression using sage :: |
194 f.simplify_full() |
273 f.simplify_full() |
196 This simplifies the expression fully . You can also do simplification |
275 This simplifies the expression fully . You can also do simplification |
197 of just the algebraic part and the trigonometric part :: |
276 of just the algebraic part and the trigonometric part :: |
198 |
277 |
199 f.simplify_exp() f.simplify_trig() |
278 f.simplify_exp() f.simplify_trig() |
200 |
279 |
|
280 .. #[Madhu: Separate lines?] |
201 |
281 |
202 One can also find roots of an equation by using find_root function:: |
282 One can also find roots of an equation by using find_root function:: |
203 |
283 |
204 phi = var('phi') find_root(cos(phi)==sin(phi),0,pi/2) |
284 phi = var('phi') find_root(cos(phi)==sin(phi),0,pi/2) |
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285 |
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286 .. #[Madhu: Separate lines?] |
205 |
287 |
206 Lets substitute this solution into the equation and see we were |
288 Lets substitute this solution into the equation and see we were |
207 correct :: |
289 correct :: |
208 |
290 |
209 var('phi') f(phi)=cos(phi)-sin(phi) |
291 var('phi') f(phi)=cos(phi)-sin(phi) |
210 root=find_root(f(phi)==0,0,pi/2) f.substitute(phi=root) |
292 root=find_root(f(phi)==0,0,pi/2) f.substitute(phi=root) |
211 |
293 |
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294 .. #[Madhu: Separate lines?] |
212 |
295 |
213 as we can see the solution is almost equal to zero . |
296 as we can see the solution is almost equal to zero . |
214 |
297 |
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298 .. #[Madhu: So what?] |
215 |
299 |
216 We can also define symbolic matrices :: |
300 We can also define symbolic matrices :: |
217 |
301 |
218 |
302 |
219 |
303 |
220 var('a,b,c,d') A=matrix([[a,1,0],[0,b,0],[0,c,d]]) A |
304 var('a,b,c,d') A=matrix([[a,1,0],[0,b,0],[0,c,d]]) A |
221 |
305 |
222 |
306 .. #[Madhu: Why don't you break the lines?] |
223 Now lets do some of the matrix operations on this matrix :: |
307 |
224 |
308 Now lets do some of the matrix operations on this matrix |
225 |
309 |
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310 .. #[Madhu: Why don't you break the lines? Also how do you connect |
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311 this up? Use some transformation keywords in English] |
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312 :: |
226 A.det() A.inverse() |
313 A.det() A.inverse() |
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314 |
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315 .. #[Madhu: Why don't you break the lines?] |
227 |
316 |
228 You can do :: |
317 You can do :: |
229 |
318 |
230 A.<Tab> |
319 A.<Tab> |
231 |
320 |
232 To see what all operations are available |
321 To see what all operations are available |
233 |
322 |
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323 .. #[Madhu: Sounds very abrupt] |
234 |
324 |
235 {{{ Part of the notebook with summary }}} |
325 {{{ Part of the notebook with summary }}} |
236 |
326 |
237 So in this tutorial we learnt how to |
327 So in this tutorial we learnt how to |
238 |
328 |
245 diff() and integrate() for calculus operations . |
335 diff() and integrate() for calculus operations . |
246 Finding roots , factors and simplifying expression using find_root(), |
336 Finding roots , factors and simplifying expression using find_root(), |
247 factor() , simplify_full, simplify_exp , simplify_trig . |
337 factor() , simplify_full, simplify_exp , simplify_trig . |
248 Substituting values in expression using substitute function. |
338 Substituting values in expression using substitute function. |
249 And finally creating symbolic matrices and performing operation on them . |
339 And finally creating symbolic matrices and performing operation on them . |
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340 |
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341 .. #[Madhu: See what Nishanth is doing. He has written this as |
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342 points. So easy to read out while recording. You may want to |
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343 reorganize like that] |