Exam 7: Locus and Concurrence
-Use the drawing provided to explain the following theorem.
"The three angle bisectors of the angles of a triangle are concurrent."
Given:
,
, and
are the angle bisectors of the angles of
Prove:
,
, and
are concurrent at point Z








Let point Z name the point of intersection of the angle bisectors and
. Because
bisects
, every point on
(including Z) is equidistant from the sides of
.
With and
, it follows that
. With respect to
, also note
that . Because Z lies on angle bisector
, we also have
. By the Transitive Property of Congruence,
. With point Z being equidistant from the sides of
, Z must also lie on angle bisector
. Thus,
,
, and
are concurrent at point Z.
-Supply missing reasons for the following proof.
Given:
bisects
;
and
Prove:
S1.
bisects
; R1.
and
S2.
R2.
S3.
and
are rt.
R3.
S4.
R4.
S5.
R5.
S6.
R6.
S7.
R7.


















R1. Given
R2. Definition of angle-bisector
R3. Perpendicular lines form right angles.
R4. All right angles are congruent.
R5. Identity
R6. AAS
R7. CPCTC
-Supply missing statements and missing reasons for the following proof.
Given: Point X not on
so that
Prove: X lies on the perpendicular-bisector of
S1. R1.
S2.
R2.
S3. With M the midpoint of
, R3.
draw
S4. Then
R4.
S5. Also,
R5.
S6. R6. SSS
S7.
R7.
S8. R8. Definition of perpendicular-bisector of a line segment










S1. Point X not on so that
R1. Given
R2. Definition of congruent line segments
R3. Through 2 points, there is exactly one line.
R4. Definition of midpoint of line segment
R5. Identity
S6. R7. CPCTC
S8. X lies on the perpendicular-bisector of
-Use the drawing provided to explain the following.
Given:
,
, and
are the medians of
Prove: 






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