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Prove That: Cos 24° + Cos 55° + Cos 125° + Cos 204° + Cos 300° = 1 2 - Mathematics

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प्रश्न

Prove that: cos 24° + cos 55° + cos 125° + cos 204° + cos 300° = \[\frac{1}{2}\]

उत्तर

 LHS =\[ \cos 24^\circ + \cos 55^\circ + \cos 125^\circ + \cos 204^\circ + \cos 300^\circ\]
\[ = \cos 24^\circ + \cos \left( 90^\circ - 35^\circ \right) + \cos \left( 90^\circ e \times 1 + 35^\circ \right) + \cos \left( 90^\circ \times 2 + 24^\circ \right) + \cos \left( 90^\circ \times 3 + 30^\circ \right)\]
\[ = \cos 24^\circ + \sin 35^\circ - \sin 35^\circ e - \cos 24^\circ + \sin 30^\circ \]
\[ = 0 + 0 + \frac{1}{2}\]
\[ = \frac{1}{2}\]
= 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 2.3 | पृष्ठ ३९

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