The problem is:

Solve each of the following equations over the interval [0,2Pi).

2sin^2 x - 1 = 0

The answers are:

Pi/4, 3Pi/4, 5Pi/4, 7Pi/4

I know how to get the first two answers, but I'm not sure how you get the last two answers, since sin would be negative in quadrants 3 and 4.

Much help appreciated. Thanks.

2 answers

Well, remember that a square root has both +- roots.
Wouldn't the last two answers be negative then?