The Law of Sines.  

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A standard cofunction involving tangent and cotangent.

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The reciprocal identity for secant.  

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A cofunction identity involving sine and cosine.

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One of the three standard identities for the cosine of a double angle.  

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The basic sine function.

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The standard identity for the sine of a double angle.  

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The standard identity for the tangent of a double angle.  

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The standard identities for the sine and cosine of a half angle.  

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A common form of the Law of Cosines.

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The definition of the tangent function.  

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The standard identities for the tangent of a half angle.  

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A laughably incorrect trigonometric identity.

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One of the three standard identities for the cosine of a double angle.  

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One of the three standard identities for the cosine of a double angle.  

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The standard identity for the sine of a difference of angles.

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