Third Angle Theorem it two angles of a triangle are to two angles of another triangle, then the third angles of those triangles are also sABC, miA+mt3+mC= 6} Practice: Using Vlllal Cues FDIIUW these steps to find the measures of angles m and n in the two triangles at right. 1. Start with the small triangle. Use the triangle sum theorem to find the measure of angle m. 2. Identihr oonoruent anoies in the Mo trianoles