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Pythagorean Identity


Videos and lessons to help High School students learn how to prove the Pythagorean identity sin2(θ) + cos2(θ) = 1 and use it to find sin(θ), cos(θ), or tan(θ) given sin(θ), cos(θ), or tan(θ) and the quadrant of the angle.

Common Core: HSF-TF.C.8

Related Topics:
Common Core (Functions)

Common Core for Mathematics

Pythagorean Identity
Informal proof and applications of the Pythagorean Identity, that sin2(θ) + cos2(θ) = 1.
Pythagorean trig identity from unit circle.

Examples using Pythagorean identities to simplify trigonometric expressions.
Using the Pythagorean trig identity.

Finding exact values using Pythagorean Identity.

Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

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