The Unit Circle Definition of Trigonometric Function

Videos, worksheets, games and acivities to help Algebra II students learn
the unit circle definition of trigonometric function.

The Definitions of Sine and Cosine
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The right triangle definitions of sine and cosine only apply to acute angles, so a more complete definition is needed. The point where the terminal side intersects the unit circle (x, y) is the basis for this definition. Since the radius (and therefore hypotenuse of the right triangle) is 1, the denominators cosine = adjacent/hypotenuse and sine = opposite/hypotenuse are also 1. Thus, the definition is y = sine and x = cosine.

How we define sine and cosine for all angle measures using the unit circle.

Unit Circle Definition of Trig Functions
Using the unit circle to define the sine, cosine, and tangent functions

The unit circle definition of trigonometric function
Using the unit circle to extend the SOH CAH TOA definition of the basic trigonometric functions.

Deriving Values on the Unit Circle.
This video shows how to derive the values in the first quadrant of the unit circle.

A Trick to Remember Values on The Unit Circle
This video shows a little 'trick' to remember the values on the unit circle in the first quadrant.

A way to remember the Entire Unit Circle for Trigonometry.

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