Question

Value of theta when cos theta=root3-1/2 theta=root3-1/2root2

Answer 1

Cos 15° = cos (45° -30°)

and cos (A-B ) = cos A cos B + sinA sin B

      = cos 45° cos 30° + sin 45° sin 30°

      =(1/√2)×(√3/2) + (1/√2)×(1/2)

      =(√3/2√2) + (1/2√2)

      = (√3+1)/2√2

yes, cos 15° = = (√3+1)/2√2