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Geometry Section 5.3 Proving Triangles Congruent by SAS What you will learn: 1.Use the Side-Angle-Side Congruence Theorem 2. Solve real-life problems To show that two triangles are congruent using the definition of congruent polygons, as we did in the proof at the end of section 5.2, we need to show that all ______ 6 pairs of corresponding parts are congruent. Theorem 5.5 allows us to prove triangles congruent using only ______ 6 pairs of corresponding parts. Before we look at Theorem 5.5, however, we need to discuss what is meant by an included angle. is formed by the 2 sides PE I two sides and the included angle two sides and the included angle Notice there are two triangles with an angle of 25 and sides of lengths 19 and 8, but the triangles are not congruent. Example 2: Determine whether each pair of triangles can be proven congruent by using the congruence postulates. If so, write a congruence statement and identify the postulate used. None is a possible answer. SAS ATR CKR NOT SAS No congruent triangles SAS ETI GHI SAS GRF GRO 1) BC DA, BC || AD 1)Given 2)BCA CAD 2)Alt. Int. Angles Theorem 3) AC AC 3)Reflexive Prop. )ABC CDA ) SAS HW: pp 249 -250 / 6-17, 23, 26