Trigonometry


THEOREM    \(\sin A = \dfrac{1}{\csc A}\)

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THEOREM    \(\cos A = \dfrac{1}{\sec A}\)

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THEOREM    \(\tan A = \dfrac{1}{\cot A}\)

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THEOREM    \(\cos 0 = 1\)

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THEOREM   

The cosine function is even.

$$\cos \theta = \cos (-\theta)$$

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THEOREM    \(\sin (-\theta) = -\sin \theta\)

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THEOREM    \(\sin \theta = \sin (\pi - \theta)\)

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THEOREM    \(\cos \theta = -\cos (\pi - \theta)\)

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THEOREM    \(\sin (\theta + \pi) = -\sin \theta\)

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THEOREM    \(\cos (\theta + \pi) = -\cos \theta\)

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THEOREM    \(\tan (\theta + \pi) = \tan \theta\)

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THEOREM    \(\tan (-\theta) = -\tan \theta\)

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THEOREM    \(\tan (\pi-\theta) = -\tan \theta\)

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