Internal bisector of angle A of triangle ABC meets side BC at D. Through D,a line drawn perpendicular to AD intersects the side AC at E and the side AB at F.If a,b,c represent the sides of triangle ABC, THEN
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AE IS H.M. OF b and c
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AD=[2bc/b+c ]cosA/2
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EF=[4bc/b+c]sinA/2
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The triangle AEF is isosceles.