Solve for x and y: 43° 75° y° x° 75° = y + 43° 75 – 43 = y 32° = y z° x and 43° are Alternate Interior Angles 43° = x

4.2 Congruence and Triangles Objective: Show that figures are congruent and identify corresponding parts of congruent triangles

What are the corresponding parts Given that ABC ≅ DEF Name all corresponding parts

Congruence Statements When you write a congruence statement for two polygons, always list the corresponding vertices in the same order. ABC ≅ DEF <CBA ≅ <FED Name the other congruent parts.

Theorem 4.3: Third Angle Theorem StatementReason <B ≅ <I and <A ≅ <H Given m<C = 57°Triangle Sum Theorem m<J = 57°Triangle Sum Theorem <C ≅ <J Definition of Congruent Angles

Properties of Congruent Triangles Reflexive Property of Congruent Triangles ABC ≅ ABC Symmetric Property of Congruent Triangles If ABC ≅ DEF then DEF ≅ ABC Transitive Property of Congruent Triangles If ABC ≅ DEF and DEF ≅ JKL Then ABC ≅ JKL

What must you show to prove two triangles are congruent All three angles in one triangle must be congruent to the three angles in the second triangle All three sides must be congruent to the three sides of the second triangle

Homework 11/4 4.2 p.228 # 1-15 odds