The trigonometric equation is $\"\"$ .

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Left hand side : $\"\"$

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$\"\"$

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$\"\"$

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Pythagorean identity : $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Trigonometric function: tan x = sin x/cos x.

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$\"\"$

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$\"\"$

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= Right hand side.