Sine function

Overview


The sine function expresses the relationship between lengths of right triangle. Specifically, the sine of an angle {% \theta %} is the ratio of the length of the opposite side of the triangle divided by the length of the hypoteneuse.

Relationship to Circle


A particularly instructive way to understand the sine is to plot a circle with radius 1. A point is chosen on the circle, where the very far right point is assigned a {% \theta=0 %}. Then the sine is equal to the projection of the selected point on the y-axis.