Question

Is it write to say cos (60°+30°) =cos 60°.cos 30°-sin 60°.sin 30°

Answer 1

Answer:

ya ,this is correct as it is resembling a formula which is

cos(A + B) = cosAcosB - sinAsinB

hope it helps you

Answer 2

Answer:

Yes, cos (A+ B) = cos A cos B - sin A sinB

here A = 60° and B = 30°

it can also be verified as mentioned below

LHS = cos90° = 0

RHS = cos 60° cos 30° - sin 60° son 30°

= 1/2*√3/2 - √3/2*1/2

= √3/4 - √3/4

= 0 = LHS