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If sin⁡θ−3cos⁡θ=0\sin \theta - \sqrt3 \cos \theta = 0 sinθ−3​cosθ=0 (θ\thetaθ​ is an acute angle), then the value of sin⁡2θ−cos⁡2θ\sin^2\theta -
Question

If sinθ3cosθ=0\sin \theta - \sqrt3 \cos \theta = 0 (θ\theta​ is an acute angle), then the value of sin2θcos2θ\sin^2\theta - \cos^2 \theta is:

A.

1

B.

12- \frac{1}{2}​​

C.

12\frac{1}{2}​​

D.

312\frac{\sqrt3 -1}{2}​​

Correct option is C

Given: 
sinθ3cosθ=0\sin \theta - \sqrt 3\cos \theta = 0 
To find: Value of sin2θcos2θ\sin^2 \theta - \cos^2 \theta 
Formula Used: 
 sinθcosθ=tanθ\ \frac{\sin \theta}{\cos \theta} = \tan \theta   
Solution: 
sinθ3cosθ=0sinθ=3cosθsinθcosθ=3tanθ=3 θ=60\sin \theta - \sqrt3 \cos \theta = 0 \\ \sin \theta = \sqrt3 \cos \theta \\ \frac{\sin \theta}{\cos \theta} = \sqrt3 \\ \tan \theta = \sqrt3 \\ \implies \theta = 60^\circ 
Putting the value of θ=60\theta = 60^\circ 
=sin260cos260=(32)2(12)2 =3414 =12=\sin^2 60^\circ - \cos^2 60^\circ \\ =\left(\frac{\sqrt3}{2}\right)^2 - \left(\frac{1}{2}\right)^2 \\ \ \\ = \frac{3}{4} - \frac{1}{4} \\ \ \\ =\bf \frac{1}{2}​​​​

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