JEE Math Practice Question

If $$x = \sum\limits_{n = 0}^\infty {{{\left( { - 1} \right)}^n}{{\tan }^{2n}}\theta } $$ and $$y = \sum\limits_{n = 0}^\infty {{{\cos }^{2n}}\theta } $$ for 0 < $$\theta $$ < $${\pi \over 4}$$, then :

1. A.x(1 + y) = 1
2. B.y(1 – x) = 1
3. C.y(1 + x) = 1
4. D.x(1 – y) = 1