Sine is the opposite over the hypotenuse; cosine is the adjacent over the hypotenuse; and tangent is the opposite side over the adjacent side. Aha, now you see why there's an abbreviation.

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Verifying Trig Identities 
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Tangent HalfAngle Formula 
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Special Right Triangles 
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SOHCAHTOA 
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Sines 
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Cosines 
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Law of Sines 
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Law of Cosines