2cos^2a*cos^2b+2sin^asin^b-1=cos2acos2b how to prove it
2 answers
You seem to have omitted exponents in the 2sin^asin^b term
2cos^2a*cos^2b+2sin^2asin^2b-1=cos2acos2b you are right... if you know how to prove it please help me