Interactive Cosine Function

This interactive demonstrates the connection between a right triangle of hypotenuse one and the graph of the cosine function. Click and drag either point to change the angle that describes the right triangle, or change the angle in the input box.

Displays the form of a right triangle. Labels the three sides: adjacent, opposite, hypotenuse. Shows that the adjacent and opposite sides are perpendicular to each-other.

It is important to note that the adjacent side of the triangle corresponds to the x component of the point. This is because the circle’s center is at the point (0,0), separate from the graph. Also, that the definition of cosine simplifies since the hypotenuse is one.

This image shows the notation for a right triangle placed in the cartesian plane.