Locus of the point of intersection of the lines `xcosalpha+ysinalpha=a` and `xsinalpha-ycosalpha=b` where `alpha` is variable.
A. `2 (x^(2) + y^(2)) = a^(2) + b^(2)`
B. `x^(2) - y^(2) = a^(2) - b^(2)`
C. `x^(2) + y^(2) = a^(2) + b^(2)`
D. none of these
