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Trigonometric Identities

★★★☆☆High School

📖Definition

Trigonometric identities are equations involving trigonometric functions that hold true for all angles.

sin²θ + cos²θ = 1

Pythagorean identity

sin(A ± B) = sin A cos B ± cos A sin B

Sine addition formula

cos(A ± B) = cos A cos B ∓ sin A sin B

Cosine addition formula

sin 2θ = 2sinθcosθ

Double angle formula (sine)

cos 2θ = cos²θ - sin²θ

Double angle formula (cosine)

예제 1

Find sin 75° using special angles.

#항등식#삼각함수#identities#trigonometry