# Math Help - Help with Trigonometry-- Cos(-1)

1. ## Help with Trigonometry-- Cos(-1)

We have a test tomorrow that he hinted there is a problem we did not go over on. I actually got the answers from a friend because I got impossibly stuck. Our test is on circles but he wanted it to be adding in Soh Cah Toa again a little.

Help?
Someone please explain Cos(-1). What does it find?

2. Originally Posted by naturallynatalie
We have a test tomorrow that he hinted there is a problem we did not go over on. I actually got the answers from a friend because I got impossibly stuck. Our test is on circles but he wanted it to be adding in Soh Cah Toa again a little.

Help?
Someone please explain Cos(-1). What does it find?
It denotes the cosine of the angle if you went one radian clockwise on the cartesian plane opposed to the usual counter clockwise...it is equlivalent to $\cos(2\pi-1)$