Good evening sir / mam

In a triangle ABC , BC=AB, and angle B =80° . Then angle A is equal to

a. 80°

b. 40°

c. 50°

d. 100°

Thank you

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Solution

Dear Students,

Given : BC = AB

⇒∠A = ∠C ................ (1) (Angle opposite to equal sides are equal)
Now,
⇒∠A + ∠B + ∠C = 180 (Angle Sum property)
⇒∠A + 80 + ∠A = 180 (From (1))
⇒2 ∠A = 180 - 80
⇒2 ∠A = 100
⇒∠A = 50

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In ΔABC, BC = AB and ∠B = 80°, then ∠A is equal to:

Δ A B C

∠ B = 80^{\circ}

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∠ B = 50^{\circ}

∠ C

Δ A B C

∠ B = 80^{\circ}

∠ A

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40^{\circ}

50^{\circ}

100^{\circ}

$I n Δ A B C, BC = AB and ∠ B = 80^{\circ} . T h e n, ∠ A = ? (a) 50^{\circ} (b) 40^{\circ} (c) 100^{\circ} (d) 80^{\circ}$

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