Albert1
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Point $H$ is the orthocenter of $\triangle ABC$
prove :$HA^2+BC^2=HB^2+AC^2=HC^2+AB^2$
prove :$HA^2+BC^2=HB^2+AC^2=HC^2+AB^2$
Very nice solution.Albert said:hint:
A solutiopn of the diagrm of this problem is given,now it is obvious ,hope someone can solve it
yes, you got it !caffeinemachine said:Very nice solution.
It is clear that $PAHB$ is a parallelogram and that $PB$ is perpendicular to $BC$.
Thus $HA^2+BC^2=4R^2$, where $R$ is the radius of the circumcircle.