In a triangle ABC- AB - AC and -B - 30- Then value of - A is -

Since AB = AC, the angles opposite these sides will also be equal. Hence, ∠ B = ∠ C ⇒∠ C = 30^∘ Now using angle sum property ∠ A +∠ B + ∠ C=180^∘ ∠ A + 30^∘ + ...

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Standard VII

Mathematics

Isosceles Triangle

In a triangle...

Question

In a triangle ABC, $A B = A C$ and $∠$ B = 30 $^{\circ}$ . Then value of $∠ A$ is .

20^{\circ}

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60^{\circ}

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120^{\circ}

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50^{\circ}

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Solution

The correct option is C $120^{\circ}$
Since AB = AC, the angles opposite these sides will also be equal.

Hence, $∠ B = ∠ C$

$\Rightarrow ∠ C = 30^{\circ}$
Now using angle sum property
$∠ A + ∠ B + ∠ C = 180^{\circ}$
$∠ A + 30^{\circ} + 30^{\circ} = 180^{\circ}$
$∠ A + 60^{\circ} = 180^{\circ}$
$∠ A = 120^{\circ}$

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In a triangle ABC, AB=AC and ∠B = 30∘. Then value of ∠A is .

The correct option is C 120∘Since AB = AC, the angles opposite these sides will also be equal. Hence, ∠B=∠C ⇒∠C=30∘ Now using angle sum property ∠A+∠B+∠C=180∘ ∠A+30∘+30∘=180∘ ∠A+60∘=180∘ ∠A=120∘

In a triangle ABC, $A B = A C$ and $∠$ B = 30 $^{\circ}$ . Then value of $∠ A$ is .