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If one angle of a triangle is equal to the sum of the other two angles, then the triangle is ______. - Mathematics

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Question

If one angle of a triangle is equal to the sum of the other two angles, then the triangle is ______.

Options

  • an isosceles triangle

  • an obtuse triangle

  • an equilateral triangle

  • a right triangle

MCQ
Fill in the Blanks

Solution

If one angle of a triangle is equal to the sum of the other two angles, then the triangle is a right triangle.

Explanation:

Given, Let angle of triangle ABC be ∠A, ∠B and ∠C

Given that: ∠A = ∠B + ∠C  ...(i)

We know that in any triangle ∠A + ∠B + ∠C = 180°  ...(ii)

From equation (i) and (ii), get:

∠A + ∠A = 180°

2∠A = 180°

`∠A = (180^circ)/2`

∠A = 90°

Hence, the triangle is a right triangle.

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Chapter 6: Lines & Angles - Exercise 6.1 [Page 55]

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NCERT Exemplar Mathematics [English] Class 9
Chapter 6 Lines & Angles
Exercise 6.1 | Q 2. | Page 55
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