If $$sin 17^\circ=\frac{x}{y}$$, then the value of $$sec17^\circ-sin73^\circ$$ is :

A

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

B

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

C

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

D

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