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प्रश्न
In a ΔABC, if ∠A=l20° and AB = AC. Find ∠B and ∠C.
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उत्तर
Consider a ΔABC,
Given that ∠A = 120° and AB = AC and given to find ∠B and ∠C
We can observe that DABC is an isosceles triangle since AB = AC
⇒∠B=∠C ………(1) [Angles opposite to equal sides are equal]
We know that sum of angles in a triangle is equal to `180^@`
`⇒∠A+∠B+∠C=180^@`
⇒`∠A+∠B+∠B=180^@` [from (1)]
⇒`120^@+2∠B=180^@`
⇒`2∠B=180^@-120^@`
⇒`2∠B=60^@⇒∠B=30^@`
⇒`∠C=∠B=30^@`
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