Given a relation between sin^-1 x and cos^-1 x, find sin^-1 x and then a trigonometric value

1. A.
   $\cos\left( \frac{4a}{\pi} \right)$
2. B.
   $\sin\left( \frac{2a}{\pi} \right)$
3. C.
   $\cos\left( \frac{2a}{\pi} \right)$
4. D.
   $\sin\left( \frac{4a}{\pi} \right)$

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1. A.
   $\frac{1 - y^{2}}{2y}$
2. B.
   $\frac{1 - y^{2}}{1 + y^{2}}$
3. C.
   $1 - y^{2}$
4. D.
   $\frac{1 - y^{2}}{y\sqrt{y}}$

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1. A.
   $4\sqrt{\left( 1 - x^{2} \right)}\left( 1 - 2x^{2} \right)$
2. B.
   $4x\sqrt{\left( 1 - x^{2} \right)}\left( 1 - 2x^{2} \right)$
3. C.
   $2x\sqrt{\left( 1 - x^{2} \right)}\left( 1 - 4x^{2} \right)$
4. D.
   $4\sqrt{\left( 1 - x^{2} \right)}\left( 1 - 4x^{2} \right)$

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