Reducing fractions with pi in them

I am trying to simplify the expression

The cosine and sine functions can be reduced modulo , right? So I wrote this as

after subtracting from each of the arguments. But checking this equality with my calculator I get something different. What am I doing wrong?

Re: Reducing fractions with pi in them

Maybe something's wrong with your calculator settings. I get and

Re: Reducing fractions with pi in them

A common mistake might be at play. Make sure you are in 'radian' mode.

-Dan

Re: Reducing fractions with pi in them

Ah, I should have known! Thanks!