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§ 4.1. C. A. B. 1. Prove that the three angle bisectors of a triangle concur. D. E. I. F. C. A. B. l 1. l 2. 2. Prove that the perpendicular bisectors of a triangle concur. O. l 3. U. T. C. Q. P. O. A. B. V. R. 3. Prove that the altitudes of a triangle concur.
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§ 4.1 C A B 1. Prove that the three angle bisectors of a triangle concur. D E I F
C A B l1 l2 2. Prove that the perpendicular bisectors of a triangle concur. O l3
U T C Q P O A B V R 3. Prove that the altitudes of a triangle concur. Note that the altitudes of ∆ABC are the perpendicular bisectors of the sides of ∆PQR and using the previous problem the perpendicular bisectors concur.
B 4. Complete the proof that the exterior angle of a triangle is greater than each of its remote interior angles. D E C A Given: A – C – D and ∆ ABC Prove ACG > A G F
6. Given: AD bisects CAB and CA = CD. Prove: CD parallel to AB.
7. Segments AB and CD bisect each other at E. Prove that AC is parallel to BD. B E C D A
8. Given two lines cut by a transversal. If a pair of corresponding angles are congruent, prove that a pair of alternate interior angles are congruent. Given: l and m cut by transversal m and A = B. t Prove: A = C. B l C A m
9. Given two lines cut by a transversal. If a pair of corresponding angles are congruent, prove that the lines are parallel. Given: l and m cut by transversal m and A = B. t Prove: l and m parallel. B l C A m
11. Given triangle ABC with AC = BC and DC = EC, and EDC = EBA, prove DE is parallel to AB. Given: AC = BC and DC = EC, and EDC = EBA Prove: DE is parallel to AB.