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°