If \[{{\cos }^{-1}}x-{{\cos }^{-1}}\frac{y}{2}=\alpha \], then \[4{{x}^{2}}-4xy\cos \alpha +{{y}^{2}}\] is equal to [AIEEE 2005]

If \[{{\cos }^{-1}}x-{{\cos }^{-1}}\frac{y}{2}=\alpha \], then \[4{{x}

1.	If \[{{\cos }^{-1}}x-{{\cos }^{-1}}\frac{y}{2}=\alpha \], then \[4{{x}^{2}}-4xy\cos \alpha +{{y}^{2}}\] is equal to [AIEEE 2005]
A.	\[4{{\sin }^{2}}\alpha \]
B.	\[-4{{\sin }^{2}}\alpha \]
C.	\[2\sin 2\alpha \]
D.	\[4\]
Answer» B. \[-4{{\sin }^{2}}\alpha \]

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