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Proving Congruence SSS, SAS. Postulate 4.1 Side-Side-Side Congruence If the sides of one triangle are congruent to the sides of a second triangle, then the triangles are congruent. Postulate 4.2 Side-Angle-Side Congruence
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Proving Congruence SSS, SAS • Postulate 4.1 Side-Side-Side Congruence If the sides of one triangle are congruent to the sides of a second triangle, then the triangles are congruent. • Postulate 4.2 Side-Angle-Side Congruence If two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then the triangles are congruent.
ENTOMOLOGY The wings of one type of moth form two triangles. Write a two-column proof to prove thatFEG HIG and G is the midpoint of both Example 4-1a
Given:G is the midpoint of both FEG HIG Proof: Statements Reasons 1. 1. Given 2. 2. Midpoint Theorem 3. FEG HIG 3. SSS Example 4-1b Prove:
Write a two-column proof to prove that ABC GBC if 3. ABC GBC Proof: Statements Reasons 1. 1. Given 2. 2. Reflexive 3. SSS Example 4-1b
COORDINATE GEOMETRYDetermine whether WDV MLPfor D(–5, –1), V(–1, –2), W(–7, –4), L(1, –5), P(2, –1), and M(4, –7). Explain. Example 4-2a Use the Distance Formula to show that the corresponding sides are congruent.
Answer: By definition of congruent segments, all corresponding segments are congruent. Therefore, WDV MLP by SSS. Example 4-2b
Determine whether ABC DEFfor A(5, 5), B(0, 3),C(–4, 1), D(6, –3), E(1, –1), and F(5, 1). Explain. Answer: By definition of congruent segments, all corresponding segments are congruent. Therefore, ABC DEF by SSS. Example 4-2c
Write a flow proof. Given: Prove:QRT STR Example 4-3a
Example 4-3b Answer:
Write a flow proof. Given: . Prove:ABC ADC Example 4-3c
Proof: Example 4-3d
Example 4-4a Determine which postulate can be used to prove that the triangles are congruent. If it is not possible to prove that they are congruent, write not possible. Two sides and the included angle of one triangle are congruent to two sides and the included angle of the other triangle. The triangles are congruent by SAS. Answer: SAS
Example 4-4b Determine which postulate can be used to prove that the triangles are congruent. If it is not possible to prove that they are congruent, write not possible. Each pair of corresponding sides are congruent. Two are given and the third is congruent by Reflexive Property. So the triangles are congruent by SSS. Answer: SSS
Determine which postulate can be used to prove that the triangles are congruent. If it is not possible to prove that they are congruent, write not possible. a. Example 4-4c Answer: SAS
b. Example 4-4d Answer: not possible