Question

Plot the point given in polar coords and find the corresponding rectangular coords for the point
(-1, -3pi/4)

Answer 1

This site might help you understand how to solve this: http://www.mathsisfun.com/polar-cartesian-coordinates.html

Answer 2

The point is (√2/2, √2/2).

The way to get there is:
First, rotate around the unit circle clockwise (negative direction) starting at (0,1). Since π is halfway around, -3/4 pi will be the middle of the third quadrant. However, since its length is -1, mirror it over the origin to get to the equivalent of (1, π/4).