Cos(x) & Unit Circle - Degrees

In this animation we plot

. Here the label and unit on the horizontal is

in degrees. There is no unit on the y-axis. The y-value of the cosine function for the angle

is the x-coordinate of the point T. (Remember: the y-value of the sine function for this angle is the y-coordinate of the point T.)

Move the slider to α=45°. The

. Do you know the exact value of

? Move the slider to α=135°. The

. Do you know the exact value of

? Now, let α=–45°. Move the slider to the corresponding angle between 0° and 360°. The

. Do you know the exact value of

? Does this agree with the fact that cos(–α)=cos(α)?

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