Question

Prove that

Cos(A+B) Cos(A-B) = Cos^2 A - Sin^2B

Answer 1

REFER TO ATTACHMENT :-

in the solution I have used the formula of

cos(A+ B).

another one of

Cos( A - B) .

then again the formula used in 4th step is

Sin^2x = 1-cos^2x.

solve it with one by one step as shown in attachment and after all the right hand side which is is the result it is proved very simple in a short manner.

and after all we take common factor and solve them to get the right hand side result.