CONSTRUCTION 2 Construct an Angle Congruent to a Civen Angle Construct an angle with vertex
Q
that is congruent to
/_(D)
as shown. Procedure The construction procedure shows that
DE=QR,DF=QS
, and
EF=RS
. Therefore,
/_(/)DEF()/(_(/))=QRS
by the SSS property, so the corresponding angles
/_(D)
and
/_(Q)
are congruent. 12.2 Constructing Geometric Figures * 633 CONSTRUCTION 3 Construct a Line Parallel to a Civen Une Given point
P
and line
l
as shown, construct a line through
P
that is parallel to L . CONSTRUCTION 4 Construct a Line Perpendicular to a Civen LineGiven line
l
and point
P
not on
I
as shown, construct a line through
P
that is perpendicular to
I
. Procedure Step 1: Construct an arc at
P
that intersects
I
at two points
A
and
B
. Step 2: With the coenpuss still
=
rodius AP, construct arcs at
A
ind 8 ind let
C
be their poier of inervection. Construct the line
PC^(2)
; since
PC
is a diaponal of thombus
ABPC
, it is perperedicular so
/bar (AB)
. The construction of perpendicular lines has several applications: CHAPTER 12: Congruence, Constructions, and Similarity
◻
SA Through a Polnt Not on the Glven Une Given line
I
and point
P
not on
I
as shown, construct a line through
P
that is perpendicular to
L
. Procedure Step 1: Construct an arc at
P
that imersects I at two points
A
and
B
. Step 2: With the compass still it radius
AP
, construct ares at
A=dB
and let
C
be their point of intersection. Construst the line
PC
; since
/bar (FC)
is a diggonal of thembes ABPC, it is perpontlicufar 10 需. The construction of perpendicular lines has several applications: Nearest point
F
on a line / from a point
P
. The line through
P
thit is perpendicular to line / intersects
/
at the point
F
of
/
that ls ctosest to
P
. Whyl' I se the triangle inequalivy)
F
is called the foot of the perpendicular line from
P
, and
PF
is called the distance from
P
to
h
. Point of reflection
P^(')
of
P^(')
across mirror line
l
, The point
P^(')
on the perpendicular ko / through CONSTRUCTION 5 Construct the Line Perpendicular to a Given Line Through a Point on the Civen Line Given line
f
and point
P
on
l
as shown, construct the line throegh
P
peppendicular to
L
, Procedure Step 1: Construct two ares of equal radius centered at
P
; let
A
and
B
be their points of intersection with ? Step 2: Construct ares centered at
A
and
B
with a raliss gmiter thin AP? let
C
and
D
be their puins of intersectioe. Step 3: Construct line
m=vec(CD)
, wince
vec(CD)
is a diagoont it the thombus
ADBC
and
P
is the midpeint of diagonal
/bar (AB)
, m passes through
P
and is perpendicular to
t:vec(AB)
: that is,
m
is perpenterular sal. CONSTRUCTION 6 . Construct the Midpoint an