Need help with some trig equations?

Question

Ok been useing trig to frame roofs and need some help with some equations like for example
Cricket Common Pitch Angle = arctan (tan 18.43495° ÷ sin 55.15010°) = 22.10606°

what kind of trig is this what do i need to know to understand this type of equations

Answer 1

You must first find the value of tan 18.43495°
using the plotter of the PC you find 0.3333,
after this you search the value of sin 55.1501 you find 0.82.
Dividing 0.333/0.82 you obtain 0.406 which is the value of the expression in bracket.
finally you search the angle which has a tangent of 0.406 and you find 22.10606°