How do I convert polar coordinates (10, -pi/4) to rectangular coordinates?

1 Answer
Aug 14, 2014

The answer is (sqrt(50), -sqrt(50)).

This problem is solved using trigonometry. I like to use the mnemonic SYR, CXR, TYX (pronounced sir kicks'er ticks). sin theta=y/r, cos theta=x/r, tan theta=y/x.

So rearranging with algebra, we get x=r cos theta, y=r sin theta.

Next, substitute the polar coordinates. Make sure that your calculator is in RAD mode. However, pi/4 is a special angle that you should memorize the ratios.

x=10 cos (-pi/4), y=10 sin(-pi/4)

-pi/4 is in the fourth quadrant, this corresponds with (sqrt(50), -sqrt(50)).