Prove three high intersection of triangle and one point

Let the heights on the two sides of the triangle ABC be, ad, be, intersect at h, and extend ch to intersect AB at F, as long as it is proved that CF is perpendicular to ab;
∵BE⊥AC,AD⊥BC,
In the quadrilateral dceh, the sum of the diagonals is 180 degrees,
Four points on a circle,
∴

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