The base angle of an isosceles triangle measures 54°. what is the measure of its vertex angle?

72

Step-by-step explanation:

We know that the sum of all the angles of any triangle is 180

We have to use the above property in order to find the measurement of the vertex angle.

Now our triangle is isosceles , that is the two equal sides will be containing equal angle. One of them is given as 54

And hence the other will also be 54.

Let the vertex angle be x

180=54+54+×

180=108+×

x=180-108

x=72

Hence the vertex angle is 72