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A point moves so that the sum of the squares ofits distances from two intersecting straight lines is constant. Prove thatits locus is an ellipse. |
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Answer» OA and DB `y=ntantheta,y=-xtantheta` `xsintheta-ycostheta=0` `xsintheta+ycostheta=0` `PL^2+PM^2=lambda^2`(const) `((hsintheta-kcostheta)/sqrt(sin^2theta+cos^2theta))^2+((hsintheta+kcostheta)/sqrt(sin^2theta+cos^2theta))^2=lambda^2` `h^2sin^2theta+k^2cos^2theta=lambda^2` `h^2/((lambda^2)/(sin^2theta))+k^2/((lambda^2/cos^2theta))=1` `(x^2)/(lambda/sintheta)^2+k^2/(lambda/costheta)^2=1`. |
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