Math Refresher

Angles
that are measured relative to the positive direction of the *x *axis are
positive if they are measured in the counterclockwise direction, and negative if
measured clockwise.

Angles may be measured in degrees or radians (rad)

p rad = 180°

When
the inverse trig functions sin^{-l}, cos^{-l}, and tan^{-1}
are taken on a calculator, you must consider the reasonableness of the answer
you get, because there is usually another possible answer that the calculator
does not give. The range of operation for a calculator in taking each
inverse trig function is indicated by the red curve in the following Figures.