You can
put this solution on YOUR website!If the vertex angle of one isosceles triangle is congruent to the vertex angle of another isosceles triangle, then the triangles are similar.
I made two triangles, triangle ABC and triangle DEF
I think the given is supposed to be: angle A is congruent to angle D
AB=AC------------Definition of isosceles triangle
DE=DF------------Definition of isosceles triangle
AB/DE = AC/DF----Equals divided by Equals are Equal
ABC is similar to DEF---- SAS (sides are proportional and the included angles are congruent)
Cheers,
Stan H.