Q3 of 34 Page 113

If the vertex angle of an isosceles triangle is 50°, find the other angles.

Given: vertex angle

let ∠A = 55°


in an isosceles triangle opposite angles of opposite sides are equal.


Hence,


Let ∠B = ∠ C = x



As we know, using theorem (1), in any triangle, sum of the three interior angles is 180 °.


So,


∠A + ∠B + ∠ C = 180°


⇒ 50° + x + x = 180°


⇒ 2x = 180° - 50°


⇒ 2x = 130°


⇒ x = 65°


So, ∠B = ∠ C = 65°.


More from this chapter

All 34 →
1

In a triangle ABC, if ∠A = 55° and ∠B = 40°, find ∠C.

 2

In a right angled triangle, if one of the other two angles is 35°, find the remaining angle.

 4

The angles of a triangle are in the ratio 1:2:3. Determine the three angles.

 5

In the adjacent triangle ABC, find the value of x and calculate the measure of all the angles of the triangle.