Question

Qual o valor y, se y=cos 75° x cos 15°?

Answer 1

y = cos(75°) . cos(15°)

y = 1/2 . (cos(75° - 15°) + cos(75° + 15°)

y = 1/2 . (cos(60°) + cos(90°))

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

y = 1/2 . 1/2

y = 1/4