Opposite angles are equal, so:One of the angles can be anything between 0 and 180 degrees (exclusive). Call this "x".The opposite angle must be the same - also "x".The other two angles must be 180 - x.
They are angles that lie on the same side of the transversal outside the lines named.
Coinciding angles.
Polygons will be similar if they have the same number of sides AND all of their angles are the same. All of their angles are the same if all but one of their angles are the same because with the same number of sides the angles must add up to the same thing. All squares are similar (4 right angles and sides of equal lenght). All rectangles are similar (4 right angles). We know two triangle are similar if two or mare angles are the same, or if one angle is the same and the two adjacent sides are the same length. Variations of this last proof may apply to some other polygons.
A SQUARE A rectangle satisfies the angles but not the lengths. A rhombus satisfies the length, but not the angles. A parallelogram neither satisfies length nor angles.
Coterminal angles.
A regular polygon.
It is called an isosceles triangle.
equiangular poygon
regular
They are called regular polygons
Its called a regular polygon
A square.
a rhombus
Just call them "congruent angles".
If the angles also have the same measure, then it is called a regular polygon.
It could have:no angles the same ortwo angles the same ortwo pairs of angles which are the same.