Let the solution curve of the differential equation \( x\,dy-y\,dx=\sqrt{x^{2}+y^{2}}\,dx ,\ x>0 ,\ y(1)=0 \), be \( y=y(x) \). Then \( y(3) \) is equal to:
\( 6 \)
\( 4 \)
\( 1 \)
\( 2 \)