Properties of TriangleMedium
Question
Internal bisector of ∠A of triangle ABC meets side BC at D. A line drawn through D perpendicular to AD intersects the side AC at E and the side AB at F. If a, b, c represent sides of ᐃABC then
Options
A.AE is HM of b and c
B.AD = 

C.EF = 

D.the triangle AEF is isosceles
Solution

We have ᐃABC = ᐃABD + ᐃACD
⇒
bc sin A =
cAD sin
b × AD sin 
⇒ AD =

Again AE = AD sec

=
⇒ AE is HM of b and c.EF = ED + DF = 2DE = 2 × AD tan

=
As AD ⏊ EF and DE = DF and AD is bisector ⇒ AEF is isosceles.
Hence A, B, C and D are correct answers.
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