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    				| 1. | Locus of the point of intersection of the lines `xcosalpha+ysinalpha=a` and `xsinalpha-ycosalpha=b` where `alpha` is variable. | 
| Answer» Correct Answer - `x^2+y^2=a^2+b^2` Let (h,k) be the point of intersection of `x cosalpha+ysinalpha=a` and `xsinalpha-ycosalpha=b`. Then, `hcosalpha+ksinalpha=a` (1) `hsinalpha-kcosalpha=b` (2) Squareing and adding (1) and (2),we get `(hcosalpha+ksinalpha)^2+(hsinalpha-kcosalpha)^2=a^2+b^2` or `h^2+k^2=a^2+b^2` Hence, the locus of (h,k) is `x^2+k^2=a^2+b^2` | |