Question
Thu February 12, 2009 By:

triangles

Expert Reply
Thu March 05, 2009

Draw AE BC

AS ABC is isosceles traingle, BE = EC

In triangle ABD

AB2=AE2+BE2

In triangle ADE

AD2=AE2+ED2

Subtracting the two equations, we get

AB2-AD2=BE2-ED2

               = (BE+ED)(BE-ED)

              = BD.(BE-ED)

              = BD. (CE-ED)   (As BE=CE)

             = BD. CD

Hence, proved

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