Question

Sum and Difference Formulas, pic attached

Answer 1

This is equal to cos(a+b) right?

Answer 2

So would it be cos(12pi/35)?

Answer 3

When I plug that into my calculator it says cos(12pi/35) does not equal the eqaution they gave though

Answer 4

@SolomonZelman Do you know anything about sum and difference formula?

Answer 5

yoiu are subtracting.

Answer 6

cos(a)cos(b) + sin(a)sin(b) --> cos(a - b)

Answer 7

\({\normalsize\color{red}{ \rm \cos(\pi/5~~-\pi/7) }}\)