The Cosine Graph

Part of the Graphs of Trig Functions section of Coddy's Trigonometry journey. Lesson 7 of 51.

Plot the point's x against the angle and you get the cosine graph. It starts at its top: 1 at 0°, 0 at 90°, −1 at 180°, 0 at 270°, and 1 again at 360°. Like the sine graph it repeats every 360° (2π) and stays between −1 and 1.

$The cosine graph from -360 to 360 degrees, top at 0 degrees, bottom at 180 degrees$

It is the same wave as sine. What differs is where the wave is at 0: the sine starts on the x axis going up, the cosine starts at its highest point and crosses the axis going down at 90°.

On the graph board a wave has a dot where it crosses its middle going up, a dot on the next top, and a dot a full wave along. The sin and cos switch writes the same curve one way or the other; it does not move it. To draw a cosine, move the wave so a top sits at 0.