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If sin² B = sin a cos a then cos 2B has the value equal to |
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Answer» is the GEOMETRIC MEAN between sinα and cosα, then SIN 2 β=sinα.cosα⇒cos2β=1−2sin 2 β=1−2sinα.cosα⇒cos 2 2β=(1−sin2α) 2 Now if we simplify option A using 2sinA.cosB=sin(A+B)+sin(A−B), we get 2sin 2 ( 4π −α)2cos 2 ( 4π +α)=(2sin( 4π −α)cos( 4π +α)) 2 =(sin 2π +sin(−2α)) 2 =(1−sin2α) 2 SIMILARLY, we can verify other options. Hence option A is CORRECT. |
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