# What is Arctan (-3/4 ) ?

Jul 11, 2015

$\arctan \left(- \frac{3}{4}\right) \cong - 0.6435$ (radians)$\cong - {36.87}^{o}$
Consider a 3-4-5 triangle. Let $\alpha$ designate the smallest angle in this triangle.
$\arctan \left(- \frac{3}{4}\right) = - \alpha$
There is no nice expression for $\alpha$ as a multiple of $\pi$ or number of degrees.