Question

prove alfa+Bita=90 degree,show the maximum value of cos alfa cos bita is 1/2.

Answer 1

that's alpha and beta.
I'll use x and y for ease of typing.

since the angles are complementary, cos(x) = sin(y)

cos(x)*cos(y)
= sin(y)*cos(y)
= 1/2 sin(2y)

since sin has maximum value of 1, ...

Answer 2

not so good answer