Simple question

• September 16th 2013, 02:29 PM
sakonpure6
Simple question
I know this is kind of dumb but cos(-x) = - cos (x) ? Right?
• September 16th 2013, 02:49 PM
Plato
Re: Simple question
Quote:

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 $\cos(x)=\cos(-x)~.$
• September 16th 2013, 02:55 PM
sakonpure6
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!!!!