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प्रश्न
Prove the following.
(secθ + tanθ) (1 – sinθ) = cosθ
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उत्तर
\[\left( \sec\theta + \tan\theta \right)\left( 1 - \sin\theta \right)\]
\[ = \left( \frac{1}{\cos\theta} + \frac{\sin\theta}{\cos\theta} \right)\left( 1 - \sin\theta \right)\]
\[ = \left( \frac{1 + \sin\theta}{\cos\theta} \right)\left( 1 - \sin\theta \right)\]
\[ = \frac{1 - \sin^2 \theta}{\cos\theta}\]
\[ = \frac{\cos^2 \theta}{\cos\theta} \left( \sin^2 \theta + \cos^2 \theta = 1 \right)\]
\[ = \cos\theta\]
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