Question

Cos(75 degrees)cos(15 degrees)

Answer 1

so like the answer is .25

Answer 2

1/4

Explanation:

The product to sum identity is useful here:

cos(α)cos(β) = (1/2)(cos(α+β) +cos(α-β))

cos(75°)cos(15°) = (1/2)(cos(90°) +cos(60°))

= (1/2)(0 + 1/2)

= 1/4

This product of cosines is 1/4.