Math basics › Trigonometry
SOH CAH TOA
The three ratios
sin = opposite/hypotenuse, cos = adjacent/hypotenuse, tan = opposite/adjacent.
Opposite and adjacent depend on the angle
They swap when you look at the other acute angle. Label the triangle for the angle you are actually using.
Finding an angle
Use the inverse: sin⁻¹, cos⁻¹, tan⁻¹. That is asking “which angle has this ratio?”