Question

Rewrite the expression as the sine or cosine of a single angle sin pi /3 cos pi/7 - cos pi/ 2 sin pi/7

Answer 1

Did you by any chance mistype sin(pi/3) or cos(pi/2)?
That would make it considerably easier :p

Answer 2

Well yes, It"s supposed to be pi/3 cos pi/7 - cos pi/ 3 sin pi/7 :)

Answer 3

Then this will help: http://www.mathwords.com/s/sum_difference_identities.htm
It's a special case. Do tell if you still need help.

Answer 4

I got sin 4pi / 21 . Is that correct?

Answer 5

Yes i believe it is

Answer 6

Thanks