Question

prove that : cos (x+Y). cos (X-Y) = cos^2Y - sin^2 x​

Answer 1

Answer:

SEE THE SOLUTION

Step-by-step explanation:

cos(x+y).cos(x-y)

={cosxcosy-sinxsiny}.{cosxcosy+sinxsiny}

=(cos^2xcos^2y)+ (cosxcosysinxsiny) - (sinxsinycosxcosy) - (sin^2xsin^2y)

=(cos^2xcos^2y)-(sin^2xsin^2y)

={cos^2x(1-sin^2y)} - {(1-cos^x)sin^2y}

=cos^2x - cos^2xsin^2y - sin^2y +sin^2ycos^2x

=cos^2x-sin^2y

HOPE IT HELPS.....

Answer 2

Step-by-step explanation:

here it is......

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