The trig function cosine,
which is written cos θ.
For acute angles, cos θ can
be found by the SOHCAHTOA definition,
shown below on the left. The
circle definition, a generalization
of SOHCAHTOA, is shown below on the right. f(x)
= cos x is
a periodic function with period 2π.
Inverse cosine, sinusoid, angle