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Write the value of sin A cos (90° − A) + cos A sin (90° − A). |
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Answer» To find: sin A cos (90° − A) + cos A sin (90° − A) ∵ cos (90° – A) = sin A and sin (90° – A) = cos A ……………(i) ∴ sin A cos (90° − A) + cos A sin (90° − A) = sin A sin A + cos A cos A [Using (i)] = sin2A + cos2A Now, ∵ sin2 θ + cos2 θ = 1 ∴ sin A cos (90° − A) + cos A sin (90° − A) = sin2A + cos2A = 1 |
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