Rotating a Line w.r.t Origin and an Endpoint

Assignment 10
Rotating a given point in a anticlockwise direction about the origin in 2D.

(You can specify a point by the left mouse button, and click the right mouse button to rotate it).
Write a program to rotate any  line  through an angle (say 30^o) with respect to

1.  the origin [Answer]
2.  one of its end points [Answer]