Question

Verify the identity. cos (x - y) - cos (x + y) = 2 sin x sin y

Answer 1

try substituting and prove

Answer 2

So I should do this:

(cos x*cos y+sin x*sin y)-(cos x*cos y + sin x.sin y)= 2sin xsiny?

Answer 3

Hello?

Answer 4

hi

Answer 5

I'm really lost. Math isn't my strongest subject area. Any chance you could give me some idea if I'm doing this right? Please and thank you!