Answer:
Congruent triangles has the two angles of one of their sides equal
This means if a triangle side has angles of 30 and 60 degrees the other triangle also has 30 and 60 degrees.
An isoceles triangle will have 2 angles of the same degree. Thus, If triangle A is isoceles then, two angles add up to make the third equal to one these two.
We should remember that angles inside a triangle always add up to 180ª
2a +b = 180
a + b = 180 - a
if the other triangle has 2 angles mathing the isoceles triangle, then it is also an isoceles.
Uploaded an image of an isoceles triangle to understand better.
Explanation:
