# Thread: solve w/o calc inverse of tan -1 and for sin,cos

1. ## solve w/o calc inverse of tan -1 and for sin,cos

how would I solve tan^-1 (-1)
i also have to do it for sin and cos

thanks

2. Think about it. If $tan(y/x)=1$, then y=x

So, it is a 45 degree angle or Pi/4 radians.