McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
3. Arcs and Chords
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Exercise 24 Page 738

Use the Hypotenuse-Leg Congruence Theorem and the definitions of bisector and arc bisector.

Statements
Reasons
1.
⊙ P and KM⊥JP
1.
Given
2.
∠ PLK and ∠ PLM are right angles
2.
Definition of perpendicular segments
3.
∠ PLK ≅ ∠ PLM
3.
All right angles are congruent
4.
LP≅LP
4.
Reflexive Property of Congruence
5.
KP≅ MP
5.
All radii of a circle are congruent
6.
△ LKP ≅ △ LMP
6.
Hypotenuse-Leg Congruence Theorem
7.
LK ≅ LM and ∠ KPL ≅ ∠ MPL
7.
Definition of congruent triangles
8.
JP bisects KM
8.
Definition of bisector
9.
m∠ KPL=m∠ MPL
9.
Definition of congruent angles
10.
mKJ = m∠ KPL and mJM=m∠ MPL
10.
Definition of arc measures
11.
mKJ = mJM
11.
Substitution
12.
JP bisects KM
12.
Definition of arc bisector
Practice makes perfect

Let's consider a circle centered at P, a chord KM, and a radius JP such that KM⊥ JP.

Next, let's draw the radii KP and MP which are congruent. Also, LP≅LP by the Reflexive Property of Congruence.

Next, since △ LKP and △ LMP are right triangles, we can apply the Hypotenuse-Leg Congruence Theorem to conclude that these triangles are congruent. △ LKP ≅ △ LMP ↙ ↘ LK ≅ LM ∠ KPL ≅ ∠ MPL We can conclude that L is the midpoint of KM and that JP bisects KM. Also, by the definition of arc measure, we can write the following two equations. mKJ = m∠ KPL mJM = m∠ MPL Since the measures written on the right-hand side are equal, we conclude that both arcs have the same measure. This implies that JP bisects KM.

Two-Column Proof

Given: & ⊙ P, KM⊥JP Prove: & JP bisectsKMandKM Let's summarize the proof we did in the following two-column table.

Statements
Reasons
1.
⊙ P and KM⊥JP
1.
Given
2.
∠ PLK and ∠ PLM are right angles
2.
Definition of perpendicular segments
3.
∠ PLK ≅ ∠ PLM
3.
All right angles are congruent
4.
LP≅LP
4.
Reflexive Property of Congruence
5.
KP≅ MP
5.
All radii of a circle are congruent
6.
△ LKP ≅ △ LMP
6.
Hypotenuse-Leg Congruence Theorem
7.
LK ≅ LM and ∠ KPL ≅ ∠ MPL
7.
Definition of congruent triangles
8.
JP bisects KM
8.
Definition of bisector
9.
m∠ KPL=m∠ MPL
9.
Definition of congruent angles
10.
mKJ = m∠ KPL and mJM=m∠ MPL
10.
Definition of arc measures
11.
mKJ = mJM
11.
Substitution
12.
JP bisects KM
12.
Definition of arc bisector