If side BC of a triangle ABC is extended to D and - ACD - 120- then - A - - B - -

The nbsp;exterior angle of a triangle is equal to the sum of the opposite interior angles. Since nbsp;the exterior angle = 120^∘, the sum of the two inter ...

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Standard IX

Mathematics

Parallel Lines with Transversal

If side BC of...

Question

If side BC of a triangle ABC is extended to D and $∠ A C D = 120^{\circ}$ , then $∠ A + ∠ B =$ .

120^{\circ}

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100^{\circ}

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60^{\circ}

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Solution

The correct option is A $120^{\circ}$

The exterior angle of a triangle is equal to the sum of the opposite interior angles.

Since the exterior angle = 120 $^{\circ}$ , the sum of the two interior angles is also 120 $^{\circ}$ .
Thus, (x+y) = $∠ A + ∠ B$ = 120 $^{\circ}$

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If side BC of a triangle ABC is extended to D and ∠ACD=120∘, then ∠A+∠B= .

The correct option is A 120∘ The exterior angle of a triangle is equal to the sum of the opposite interior angles. Since the exterior angle = 120∘, the sum of the two interior angles is also 120∘. Thus, (x+y) =∠A+∠B = 120∘

If side BC of a triangle ABC is extended to D and $∠ A C D = 120^{\circ}$ , then $∠ A + ∠ B =$ .

The correct option is A $120^{\circ}$

The exterior angle of a triangle is equal to the sum of the opposite interior angles.

Since the exterior angle = 120 $^{\circ}$ , the sum of the two interior angles is also 120 $^{\circ}$ .
Thus, (x+y) = $∠ A + ∠ B$ = 120 $^{\circ}$