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If cos ∅ - sin ∅ =√2 sin∅, prove that cos ∅ + sin∅ =√2 cos∅

Answer»

Here I am WRITING Ф as A because it is difficult for me to WRITE Ф Always.

Given : cos A - sin A =  (\sqrt{2} sin A)

On SQUARING both sides, we get

(cos A - sin A)^2 = ( \sqrt{2} sin A)^2

cos^2A+ sin^2A - 2sinAcosA = 2sin^2 A

cos^2A = sin^2A + 2sinAcosA

Add cos^2A on both sides, we get

cos^2 A + cos^2A = sin^2A + cos^2A + 2sinAcosA

2cos^2A = (cosA+sinA)^2

\sqrt{2} cos A = (cos A + sin A)



Hope this HELPS!



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