Question

prove that cos(a+b).cos(a-b) = 1-(sin^a+sin^b)

Answer 1

^ does this mean to the power ?

Answer 2

it is the square

Answer 3

cos(a+b).cos(a-b)=(cos2a+cos2b)/2
=1/2*[1-2sin^2a+1-2sin^2b]
=1/2*2[1-(sin^2a+cos^2b)]
=1-(sin^2a+cos^2b)

Answer 4

did you get the previous solution?

Answer 5

* does it mean multiplication ?

Answer 6

yes

Answer 7

you could work this way too
cos(A+B).cos(A-B)
=(cosA cos B - sinAsinB)(cosA cos B +sinAsinB)
and then multiply the terms

Answer 8

@RED123url : i can't answer the questions :(