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Prove That: Tan (−225°) Cot (−405°) −Tan (−765°) Cot (675°) = 0 - Mathematics

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प्रश्न

Prove that: tan (−225°) cot (−405°) −tan (−765°) cot (675°) = 0

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उत्तर

LHS =\[ \tan \left( - 225^\circ \right) \cot \left( - 405^\circ \right) - \tan \left( - 765^\circ \right) \cot \left( 675^\circ \right)\]
\[ = \left[ - \tan \left( 225^\circ \right) \right]\left[ - \cot \left( 405^\circ \right) \right] - \left[ - \tan \left( 765^\circ \right) \right] \cot \left( 675^\circ \right) \left[ \because \tan \left( - x \right) = \tan \left( x \right) and \cot \left( - x \right) = - \cot \left( x \right) \right]\]
\[ = \tan \left( 225^\circ \right) \cot \left( 405^\circ \right) + \tan \left( 765^\circ \right) \cot \left( 675^\circ \right)\]
\[ = \tan \left( 90^\circ \times 2 + 45^\circ \right) \cot \left( 90^\circ \times 4 + 45^\circ \right) + \tan \left( 90^\circ \times 8 + 45^\circ \right) \cot \left( 90^\circ \times 7 + 45^\circ \right)\]
\[ = \tan \left( 45^\circ \right) \cot \left( 45^\circ \right) + \tan \left( 45^\circ \right)\left[ - \tan \left( 45^\circ \right) \right]\]
\[ = 1 \times 1 + 1 \times \left( - 1 \right)\]
\[ = 1 - 1\]
\[ = 0\]
RHS
Hence, proved .

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अध्याय 5: Trigonometric Functions - Exercise 5.3 [पृष्ठ ३९]

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आरडी शर्मा Mathematics [English] Class 11
अध्याय 5 Trigonometric Functions
Exercise 5.3 | Q 2.4 | पृष्ठ ३९

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