Simplify by referring to the appropriate triangle or trigonometric identity:

Question

cos(arctan(x))

Answer 1

sketch a right-angled triangle with some angle Ø
, label the opposite side x and the adjacent side 1
(this way tanØ = x/1 , and Ø = arctan(x/1)
the hypotenuse would be √(x^2 + 1)
and
cosØ = 1/√(x^2+1)