Question

find the value of cos7.5°​

Answer 1

Answer:

7½° lies in the first quadrant.

Therefore, cos 7½° is positive.

For all values of the angle A we know that, cos (α - β) = cos α cos β + sin α sin β.

Therefore, cos 15° = cos (45° - 30°)

cos 15° = cos 45° cos 30° + sin 45° sin 30°

= 1√2∙√32 + 1√2∙12

= √32√2 + 12√2

= √3+12√2