# Math Help - Simple question

1. ## Simple question

I know this is kind of dumb but cos(-x) = - cos (x) ? Right?

2. ## Re: Simple question

Originally Posted by sakonpure6
I know this is kind of dumb but cos(-x) = - cos (x) ? Right?
NO! It is not correct. $\cos(x)$ is an even function, therefore $\cos(x)=\cos(-x)~.$

3. ## Re: Simple question

Omg thank you!!! I knew that sin(-x) = - sin x but when I put in a negative value for cos say, cos (-60) i got a positive number. Thanks!!!!