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Analytical Geometry

Cool goIITian

Joined:	1 Feb 2010
Post:	32

6 Sep 2010 21:01:46 IST

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pleez any1 tell me the short trick to solve the que of type- find the image and foot of per. Of d p

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pleez any1 tell me the short trick to solve the que of type-find the image and foot of per. Of d point from line and the eq. Of the per line

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jay

Cool goIITian

Joined: 11 Nov 2008

Posts: 77

7 Sep 2010 12:42:12 IST

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Let p(x1,y1) be a point and t(a,b) be its image about a line Ax+By+C=0 . Now we have a relation,x1-a/A = y1-b/B = -2(Ax1+By1+C)/A^2+B^2 . From this u can find out a and b but this is a use less shit. If u know the distance from the line to the point then u can use parametric equation . This is a good methode to find the image. U know the line so u can get the equation of line perpendicular to it passing throug the given point and u also know the distance than use parametric equation (x1+-rcos@,y1+-rsin@) where x1 y1 is the point of intersection of the given line and the perpendicular to it. And r is the distance of point of intersection and the given point and @ is the slop of perpendicular line .

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