Fewpal
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If 7cos^2 A +3sin^2 A = 4 find value of TanA

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1 Answer

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3sin2A + 7cos2A = 4

=3sin2A + 3cos2A + 4cos2A = 4

=4cos2A + 3(sin2A + cos2A) = 4  --------(sin2A + cos2A =1)

=4cos2A + 3 = 4

=4cos2A = 4 – 3 = 1

=cos2A = 1/4

=cosA = √1/4

=cosA = 1/2

=cosA =cos60  (cos60 = 1/2)

=A = 60

Therefore tanA = √3  (tan60 = √3)

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