Question

What does `cos(arctan((-3pi)/4))` equal?

Answer 1

`cos(arctan((-3pi)/4))=4/sqrt(16+9pi^2)`

Explanation:

We are looking for the cosine function of an angle A. The angle A whose tangent =`(-3pi)/4`

`A=arctan((-3pi)/4)` it is an angle

Just imagine a right triangle with angle A with opposite side `=-3pi`
and with adjacent side `=4`. Then we have a hypotenuse `=sqrt(4^2+(-3pi)^2)=sqrt(16+9pi^2)`

`cos A=4/sqrt(16+9pi^2)`