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In a triangle ABC, AB =AC, angle BAC = ...

In a triangle ABC, AB =AC, `angle BAC = 40^@`. Then the external angle at B is :
एक त्रिभुज ABC में `AB = AC, angleBAC = 40^@` है, तो B पर बाह्य कोण कितना होगा?

A

A)`70^@`

B

B)`110^@`

C

C)`80^@`

D

D)`90^@`

Text Solution

Verified by Experts

The correct Answer is:
B
माना कि `angleABC =x^@` है (:
`:. angleBCA = x^@ ( :. AB=AC " ह ")`

`DeltaABC` में,
`x+ x + 40^@ = 180^@ implies 2x = 140^@ implies x=70^@`
`:. angleDBE=x+40^@=70^@+40^@=110^@`
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