If $$\cos \theta = \frac{x^2 - y^2}{x^2 + y^2}$$ then the value of $$\cot \theta$$ is equal to [If $$0 \leq \theta \leq 90^\circ$$]

A

$$\frac{2xy}{x^2 - y^2}$$

B

$$\frac{2xy}{x^2 + y^2}$$

C

$$\frac{x^2 + y^2}{2xy}$$

D

$$\frac{x^2 - y^2}{2xy}$$