GR-9T2-MA-CAPS-3-5-Cons-Geom-Fig-1-Revise - E

GR 9 3-5-1 ANSWERS
Page 1 of 3
NAME: ANSWERS
Gr 9
Date:
Time
½ hr.
CAPS
3-5 Construction of Geometric Figures Activity 1 Revising 90°
Reference
3-5-1 Revise constructing an angle of 90°
Topic
1.
Think First! [5 mins]
1.1
right angle
2.
Go ahead! [10 mins]
1.2
perpendicular
1.3
Learners own answers
2.1. Construct the perpendicular bisector of a line.
http://www.hegartymaths.com/ks3/all/ks3/shape-space/v/theperpendicular-bisector-of-a-line
Step 1. Draw a line e.g. AB
P
Step 2. Using the same radius with A as centre draw 2 arcs,
one above and one below the line. Repeat using B as centre
so the arcs cross. Call the points P and Q.
Q
Step 3 Draw a line through PQ. The line will bisect AB and be perpendicular to it.
P
Q
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GR 9 3-5-1 ANSWERS
2.2.
Page 2 of 3
Construct a perpendicular from a point on a line.
http://www.hegartymaths.com/ks3/all/ks3/shape-space/v/theperpendicular-from-a-point-on-a-line
Step 1 From a point, M, marked on a line
using the same radius draw arcs, K and P,
on either side of M.
K
P
M
D
Step 2 From K and P and using a larger
radius, the same for each arc, draw 2 arcs to cut above
(or below) the line at D.
K
M
P
D
Step 3 Draw a line through DM. DM will be
perpendicular to KP.
K
P
M
2.3.
Construct a perpendicular to a line from a point above or below the line.
K
Step 1 From a point, K, marked above a line
using the same radius draw arcs, F and G, on
the line.
F
G
K
Step 2 From F and G and using a larger
radius, the same for each arc, draw 2 arcs to cut
below the line at Z.
F
G
Z
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GR 9 3-5-1 ANSWERS
Page 3 of 3
K
Step 3 Draw a line through KZ. KZ will be perpendicular
to KZ.
F
G
Z
4.
Going further! [5 mins + own time]
A
B
M
C
4.4
4.5
They are the same length.
The circle goes through A, B and C.
5.
Going even further! [own time]
Learners own efforts
The point of concurrence of the perpendicular bisectors of the sides of a triangle can be used as
the centre of a circle which passes through the vertices of the triangle.
© e-classroom 2015
www.e-classroom.co.za