How do I use properties of congruence to find unknown values?

Always list the corresponding vertices in the same order. You might want to know if the angles are congruent or not for one to be able to solve your problem. Also all the angles MUSt equal to 180 degrees. When you are working with isosceles trianlges, you will always have a vertex angle, one leg on each side of a triangle, a base angle and a base. The Base angle Therom means if all the sides are congruent then the angles will be congruent. Base Angle Converse means if the bass is congruent, then the legs are congruent.Base Angle therom-Corollary, if a triangle is equilateral, then it is equilangular and The Base angle converse-Corollary, if a triangle is equilanglar, then it is equilaterial. When you are looking for properties of congruence, you will be looking for a congruent statement, corresponding angle and corresponding sides.