9.30 Chapter 9
In Book 1B Chapter 10, we learnt that in two congruent triangles,
(a) their corresponding angles are equal;
(b) their corresponding sides are equal.
Likewise,
in two congruent figures,
(a) their corresponding angles are equal;
(b) their corresponding sides are equal.
For convenience, we focus
on congruent polygons in
this section. In this section,
'congruent figures' refers to
'congruent polygons' unless
otherwise stated.
◀
As shown on the right, quadrilaterals ABCD and PQRS are congruent
figures, where:
1. +A = +P, +B = +Q, +C = +R, +D = +S,
i.e. their corresponding angles are equal.
2. AB = PQ, BC = QR, CD = RS, DA = SP,
i.e. their corresponding sides are equal.
In the above case, congruent figures ABCD and PQRS can be represented
as follows:
ABCD , PQRS
Quick Quiz
In the figure, ABCD , PQRS. Write down the corresponding angles and the
corresponding sides of the pair of congruent figures.
A D
C
B Q
P S
R
+BAD = + �+ABC = + �+BCD = + �+ADC = +
AB = BC = CD = AD =
B
A
DC
Q
P
SR
We must name the pair of congruent
figures according to the order of the
corresponding vertices, such that the
corresponding angles and sides are
identified easily.
A photocopier can make
copies of documents that
are congruent to the
original ones. Its working
principle is xerography,
which makes use of light,
electrostatic charges and
heat.
#photocopy #xerography
ET MS
Zone