Question
Asked Oct 20, 2019
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Verify the tirgonometric identity.

cos(x+y)cos(x-y)=cos^2x-sin^2y

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Expert Answer

Step 1

The given expression to be proved is,

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cos (x+y)cos (x-y) = cos' x-sin2 y

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Step 2

LHS can be evaluated as,

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cos(xy) cosxcos y -sin xsin y cos(x-y) cosrcos y + sin x sin y cos(x+ y)cos(x-y)= (cosxcos y-sin xsin y)( cosx cos y + sin x sin y) cos rcos2 ycos .xcos ysin xsin y -sin rsin ycos xcos y - sin2 xsin2 y, 'cos2 y 1-sin2 y cos xcos2 y-sin xsin2 y sin2 x1-cos2 x = cos' x(1-sin' y)-(1- cos' x)sin' y cos x-cos sin2y- sin2 y+cos' rsin2 y cos2 x-sin2 y

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Step 3

RHS can be writ...

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2 y cosx-sin

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Math

Trigonometry