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Areas Of Parallelograms And Triangles

Question
CBSEENMA9002617

AD is an altitude of an isosceles triangle ABC in which AB = AC. Show that

(i)    AD bisects BC
(ii)    AD bisects ∠A.

Solution

Given: AD is an altitude of an isosceles triangle ABC in which AB = AC.
To Prove: (i) AD bisects BC
(ii) AD bisects ∠A.
Proof: (i) In right ∆ADB and right ∆ADC,
Hyp. AB = Hyp. AC    | Given
Side AD = Side AD    | Common

∴ ∆ADB ≅ ∆ADC    | RHS Rule
∴ BD = CD    | C.P.C.T.
⇒ AD bisects BC.
(ii) ∵ ∆ADB ≅ ∆ADC
| Proved in (i) above
∴ ∠BAD = ∠CAD    | C.P.C.T.
⇒ AD bisects ∠A.