Question

A line m is perpendicular to an angle bisector of ∠A. The sides of ∠A intersect this line m at points M and N. Prove that △AMN is isosceles.

PROVE with statement and reason
pls help thanks

Answer 1

Explanation:

Given: A line m is perpendicular to the angle bisector of ∠A. We call this

intersecting point as D. Hence, in figure ∠ADM=∠ADN =90°.

AD is angle bisector of ∠A. Hence, ∠MAD=∠NAD.

To Prove: ΔAMN is an isosceles triangle. i.e any two sides in ΔAMN are

equal.

Solution: Now, In ΔADM and ΔADN

∠MAD=∠NAD ...(1) (∵Given)

AD=AD ...(2) (∵common side)

∠ADM=∠ADN ...(3) (∵Given)

Hence, from equation (1),(2),(3) ΔADM ≅ ΔADN

( ∵ ASA congruence rule)

⇒ AM=AN

Now, In Δ AMN

AM=AN (∵ Proved)

Hence, ΔAMN is an isosceles triangle.