diff -r a3aa223c1662 -r 0038edaf660c plotting_using_sage/questions.rst
--- a/plotting_using_sage/questions.rst	Fri Oct 08 23:55:07 2010 +0530
+++ b/plotting_using_sage/questions.rst	Sun Oct 10 13:42:57 2010 +0530
@@ -1,90 +1,70 @@
 Objective Questions
 -------------------
 
- 1. If ``a = [1, 1, 2, 3, 3, 5, 5, 8]``. What is set(a)
-
-   a. set([1, 1, 2, 3, 3, 5, 5, 8])
-   #. set([1, 2, 3, 5, 8])
-   #. set([1, 2, 3, 3, 5, 5])
-   #. Error
+ 1. Plot the curve ``sin(x) - cos(x)`` in the range (0, 2pi)
 
-   Answer: set([1, 2, 3, 5, 8])
-
- 2. ``a = set([1, 3, 5])``. How do you find the length of a?
-
-   Answer: len(a)
-
- 3. ``a = set([1, 3, 5])``. What does a[2] produce?
+   Answer::
 
-   a. 1
-   #. 3
-   #. 5
-   #. Error
-
-   Answer: Error
-
- 4. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
-    is the value of ``odd | squares``?
+       x = var('x')
+       plot(sin(x) - cos(x), (x, 0, 2*pi))
 
-   Answer: set([1, 3, 4, 5, 7, 9, 16])
-
- 5. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
-    is the value of ``odd - squares``?
+ 2. plot ``sin(3x)`` and ``cos(x/3)`` and show them in same figure
 
-   Answer: set([3, 5, 7])
-
- 6. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
-    is the value of ``odd ^ squares``?
+   Answer::
 
-   Answer: set([3, 4, 5, 7, 16])
-
- 7. ``odd = set([1, 3, 5, 7, 9])`` and ``squares = set([1, 4, 9, 16])``. What
-    does ``odd * squares`` give?
+       x = var('x')
+       p1 = plot(sin(3*x), (x, 0, 2*pi))
+       p2 = plot(cos(x/3), (x, 0, 2*pi))
+       show(p1+p2)
 
-   a. set([1, 12, 45, 112, 9])
-   #. set([1, 3, 4, 5, 7, 9, 16])
-   #. set([])
-   #. Error
-
-   Answer: Error
-
- 8. ``a = set([1, 2, 3, 4])`` and ``b = set([5, 6, 7, 8])``. What is ``a + b``
+ 3. plot ``cos(x)`` vs ``sin(x)^15`` in the range (-2pi, 2pi)
 
-   a. set([1, 2, 3, 4, 5, 6, 7, 8])
-   #. set([6, 8, 10, 12])
-   #. set([5, 12, 21, 32])
-   #. Error
-
- 9. ``a`` is a set. how do you check if if a varaible ``b`` exists in ``a``?
-
-   Answer: b in a
-
- 10. ``a`` and ``b`` are two sets. What is ``a ^ b == (a - b) | (b - a)``?
+   Answer::
 
-   a. True
-   #. False
-
-   Answer: False
-
+       x = var('x')
+       parametric_plot((cos(x), sin(x)^15), (x, -2*pi, 2*pi))
 
-Larger Questions
-----------------
-
- 1. Given that mat_marks is a list of maths marks of a class. Find out the
-    no.of duplicates marks in the list.
+ 4. plot tan curve in the range (-2pi, 2pi) in red colour.
+    [hint: see the documentation]
 
    Answer::
 
-     unique_marks = set(mat_marks)
-     no_of_duplicates = len(mat_marks) - len(unique_marks)
+       x = var('x')
+       p1 = plot(tan(x), (x, -2*pi, 2*pi), color=(1, 0, 0))
+       show(p1)
+
+ 5. plot ``e^(1/x^2)`` in the range (0.5, 2.5) and set the y-axis limits to (0,
+    20)
 
- 2. Given that mat_marks is a list of maths marks of a class. Find how many
-    duplicates of each mark exist.
+   Answer::
+
+       x = var('x')
+       p2 = plot(e^(1/x^2), (x, 0.5, 2.5))
+       show(p2, ymin=0, ymax=20)
+
+ 6. plot the function ``y = 5x + 3`` using dotted line in the range (-2, 2)
+    [hint: read the documentation of the function ``line``]
 
    Answer::
 
-     marks_set = set(mat_marks)
-     for mark in marks_set:
-         occurences = mat_marks.count(mark)
-         print occurences - 1, "duplicates of", mark, "exist"
+       points = [ (i, 5*i+3) for i in srange(-2,2,0.1) ]
+       l1 = line(points, linestyle=":")
+       show(l1)
+
+ 7. plot the function ``z = cos(x) + sin(y)`` for x in the range (0, 2pi) and y
+    in range (-2pi, 2pi)
+
+   Answer::
 
+       x, y = var('x y')
+       plot3d(cos(x) + sin(y), (x, 0, 2*pi), (y, -2*pi, 2*pi))
+
+ 8. Read the sage documentation and find out which function plots closed surfaces
+
+   a. parametric_plot3d
+   #. plot3d
+   #. implicit_plot3d
+   #. contour_plot
+
+   Answer: implicit_plot3d
+