Question

If A = B = 60 , verify that
cos ( A - B ) = cos A cos B + sin A sin B

Answer 1

Answer:

Step-by-step explanation:

Answer 2

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

put A= B= 60°

cos( 60°-60°) = cos 60° cos 60° + sin 60° sin60°      

cos0° = 1/2 × 1/2 +  √3/2 × √3/2

1 = 1/4 + 3/4

1= 4/4

1 = 1

L.H.S = R.H.S

Hence Proved