How do i prove that these are the vertices of an isosceles triangle: (-3,0), (0,4), (3,0)?

In an isoceles triangle two angles are equal
if u take the coordinates and apply it in the graph it makes and isoceles triangle
as the y-axis is zero two of the ends will be level and x-axis is equal on both sides of the origin so (0,4) will be the third non equal angle

Ithink it is 7. 16