two triangles coincide exactly when superposed.

a. Theorem 1. Two triangles are congruent if two sides and the included angle of one triangle

are equal to two sides and the included angle of the other triangle, as shown in Figure 3-27.

b. Theorem 2. Two triangles are congruent if a side and the adjacent angles of one triangle are

equal to a side and the adjacent angles of the other triangle, as shown in Figure 3-28, page 3-16.