Question

By using cos((a-b)=cosa cosb +sina sinb find the valueof cos 15^ considera greater b

Answer 1

Answer:

(1 + √3) / (2√2)

Step-by-step explanation:

You know that

cos 45 = sin 45 = 1/√2,

cos 30 = √3/2,  and

sin 30 = 1/2.

So

cos 15 = cos(45 - 30)

= cos 45 cos 30 + sin 45 sin 30

= (1 + √3) / (2√2)