If in an isosceles triangle, each of the base angles is 40°, then the triangle is
a. Right-angled triangle
b. Acute angled triangle
c. Obtuse angled triangle
d. Isosceles right-angled triangle

Solution:

Given, in an isosceles triangle each of the base angles is 40°.

We have to find the type of the triangle.

Consider an isosceles triangle ABC,

The base angles ∠B = 40° and ∠C = 40°.

By angle sum property of a triangle,

We know that the sum of all the three interior angles of the triangle is equal to 180 degrees.

∠A + ∠B + ∠C = 180°

∠A + 40° + 40° = 180°

∠A + 80° = 180°

∠A = 180° - 80°

∠A = 100°

An obtuse angle is defined as an angle that is greater than 90° and less than 180° i.e 90° to 180°.

∠A is greater than 90 degrees.

Therefore, ABC is an obtuse angled triangle.

✦ Try This: If in an isosceles triangle, each of the base angles is 50°. Determine the type of triangle

☛ Also Check: NCERT Solutions for Class 7 Maths Chapter 6

NCERT Exemplar Class 7 Maths Chapter 6 Problem 14

If in an isosceles triangle, each of the base angles is 40°, then the triangle is: a. Right-angled triangle, b. Acute angled triangle, c. Obtuse angled triangle, d. Isosceles right-angled triangle

Summary:

If in an isosceles triangle, each of the base angles is 40°, then the triangle is an obtuse angled triangle

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