Question

is it right to say cos (60°+30°) = cos 60° cos 30° - sin 60° sin 30°

Answer 1

yes it is true cos(a+b) =Cosa cosb-sinasinb

Answer 2

the answer is

cos(60+30)=cos(90-30).cos30-sin(90-30).sin30

cos 90= sin 30.cos30- cos30.sin30

0=1-1

0=0

therefore it is right to say that above statement is right