Q9 of 76 Page 11

In an isosceles triangle, if the vertex angle is twice the sum of the base angles, then the measure of vertex angle of the triangle is

Let the base angles be x each,

Vertex angle = 2(x + x) = 4x


Now, since the sum of all the angles of a triangle​ is 180°


x + x + 4x = 180°


6x = 180°


x = 30°


Therefore, vertex angle= 4x = 120°

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