JEE Math Practice Question

If $${{{{\sin }^1}x} \over a} = {{{{\cos }^{ - 1}}x} \over b} = {{{{\tan }^{ - 1}}y} \over c}$$; $$0 < x < 1$$, then the value of $$\cos \left( {{{\pi c} \over {a + b}}} \right)$$ is :

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