Question

How do you evaluate cos (arctan 3/4)?

Answer 1

`4/5`

Explanation:

Consider the right triangle ABC that has 2 legs, AB = 3, and BC = 4,
and `B = 90^@`
Its hypotenuse AC is 5 (Ratio of sides --> 3:4:5)
The cosine of angle C is: `cos C = (BC)/(AC) = 4/5`
There for:
cos (arctan 3/4) = 4/5