Answer :
internal measure of a triangle is 180 degrees
base angles of an isosceles triangle are =
therefore each base angle is 4x
4x+4x+x=180
9x= 180
x=20
vertex angle= 20
base angles of an isosceles triangle are =
therefore each base angle is 4x
4x+4x+x=180
9x= 180
x=20
vertex angle= 20