Triangle Congruence by ASA and AAS Skill 21b

Objective HSG-SRT.5: Students are responsible for proving two triangles are congruent by ASA and AAS.

Postulate 14 E B F C D A If ∠𝑨≌∠𝑫 , ∠𝑪≌∠𝑭 , and 𝑨𝑪 ≌ 𝑫𝑭 Then ∆𝑨𝑩𝑪≌∆𝑫𝑬𝑭 Angle-Side-Angle Postulate If two angles and the included side of one triangle aer congruent to two angles and the included side of another triangle, then the two triangles are congruent. B A C E D F If ∠𝑨≌∠𝑫 , ∠𝑪≌∠𝑭 , and 𝑨𝑪 ≌ 𝑫𝑭 Then ∆𝑨𝑩𝑪≌∆𝑫𝑬𝑭

Theorem 19 E B F C D A If ∠𝑨≅∠𝑫 , ∠𝑩≅∠𝑬 , and 𝑨𝑪 ≌ 𝑫𝑭 Then ∆𝑨𝑩𝑪≌∆𝑫𝑬𝑭 Angle-Angle-Side Theorem If two angles and a nonincluded side of one triangle are congruent to two angles and the corresponding nonincluded side of another triangle, then the two triangles are congruent. B A C E D F If ∠𝑨≅∠𝑫 , ∠𝑩≅∠𝑬 , and 𝑨𝑪 ≌ 𝑫𝑭 Then ∆𝑨𝑩𝑪≌∆𝑫𝑬𝑭

Theorem 19; AAS Theorem Given: ∠𝐴≅∠𝐷, ∠𝐵≅∠𝐸, and 𝐴𝐶 ≌ 𝐷𝐹 Prove: ∆𝐴𝐵𝐶≌∆𝐷𝐸𝐹 B A C E D F Statement Reason 1) ∠𝐴≅∠𝐷, ∠𝐵≅∠𝐸, & 𝐴𝐶 ≌ 𝐷𝐹 1) Given 2) ∠𝐶≅∠𝐹 2) 3rd Angle Thm. 3) ∆𝐴𝐵𝐶≌∆𝐷𝐸𝐹 3) ASA Postulate

Example 1; Writing a proof using ASA Post. Given: 𝐴𝐵 ≌ 𝐷𝐸 , ∠𝐴≅∠𝐷, and ∠𝐵 & ∠𝐸 are rt. ∠’s. Prove: ∆𝐴𝐵𝐶≌∆𝐷𝐸𝐹 A B C E D F Statement Reason 1) 𝐴𝐵 ≌ 𝐷𝐸 , ∠𝐴≅∠𝐷, and ∠𝐵 and ∠𝐸 are right angles. 1) Given 2) ∠𝐵≌∠𝐸 2) ≌ of Rt. ∠’s Thm. 3) ∆𝐴𝐵𝐶≌∆𝐷𝐸𝐹 3) ASA Postulate

Example 2; Using SAS Postulate a) Which triangles are congruent? Explain. S U V E N O T W A ∠𝐸≌∠𝑈 ∠𝑂≌∠𝑉 𝐸𝑂 ≌ 𝑈𝑉 (included side) ∆𝐸𝑂𝑁≌∆𝑈𝑉𝑆 by SAS Postulate

Example 2; Using SAS Postulate b) Which triangles are congruent? Explain. F N I O H G T C A ∠𝐶≌∠𝐺 ∠𝐴≌∠𝐻 𝐶𝐴 ≌ 𝐺𝐻 (included side) ∆𝐶𝐴𝑇≌∆𝐺𝐻𝑂 by SAS Postulate

Example 3; Writing a proof using ASA Post. Given: ∠𝐶𝐴𝐵≅∠𝐷𝐴𝐸, 𝐵𝐴 ≌ 𝐸𝐴 , and ∠𝐵 & ∠𝐸 are right angles. Prove: ∆𝐴𝐵𝐶≌∆𝐷𝐸𝐹 A B C E D Statement Reason 1) ∠𝐶𝐴𝐵≅∠𝐷𝐴𝐸, 𝐵𝐴 ≌ 𝐸𝐴 , and ∠𝐵 & ∠𝐸 are right angles. 1) Given 2) ∠𝐵≌∠𝐸 2) ≌ of Rt. ∠’s Thm. 3) ∆𝐴𝐵𝐶≌∆𝐷𝐸𝐹 3) ASA Postulate

#21b: Triangle Congruence by ASA & AAS Questions? Summarize Notes Homework Video Quiz