Learn the unit circle definition of trigonometric functions with Khan Academy's engaging and educational resources.

For each point on the unit circle, select the angle that corresponds to it. Click each dot on the image to select an answer.

For each point on the unit circle, select the angle that corresponds to it. Click each dot on the image to select an answer.

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Learn how to use the unit circle to define sine, cosine, and tangent for all real numbers. Created by Sal Khan.

Sal draws the graph of the tangent function based on the unit circle definition of the function.

Learn how to use the unit circle to define sine, cosine, and tangent for all real numbers. Created by Sal Khan.

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Nucleic acids, and DNA in particular, are key macromolecules for the continuity of life. DNA bears the hereditary information that’s passed on from parents to children, providing instructions for how (and …

Tau radians means we've gone all the way around the unit circle. So cosine of tau-- remember, we're back at the beginning of the unit circle right over here-- so cosine of tau is going to be equal to 1.