Page 12 - 4-Math-8 Geometry
P. 12
To measure ABC, place the protractor on the ray BC such that the vertex is
at the centre mark of the protractor. If the ray lies on the 0 of the lower scale,
we read the lower scale of the protractor. If the ray lies on the 0 of the upper
scale, we read the upper scale of the protractor. A
BC lies on the 0 of the lower scale. 70 80 90 100 110 61020 50130
So, we will read the lower scale. 110 100 90 80 70
BA falls on the marking that is 2 after 45. 50130 61020
So, ABC measures 47 degrees. 14040
We can also write it as, m ABC 47 15300 14040
15300
20160 160
20
10 170
170 10
0 180
180 0
B C
B
70 80 90 100 110 61020 50130 CD lies on 0 of the lower scale. So, we
110 100 90 80 70 read the lower scale. BC meets on 90.
50130 61020 m BCD 90
14040
15300 14040 BCD is a right angle.
15300
20 160
160 20
10 170
170 10
0 180
180 0
CD
X
70 80 90 100 110 61020 50130 YZ lies on 0 of the lower scale. So, we
110 100 90 80 70 read the lower scale. XY meets on 65.
50130 61020 m XYZ 65
14040
15300 14040 XYZ is an acute angle.
15300 Z
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20
10 170
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0 180
180 0
Y
R
70 80 90 100 110 61020 50130 QP lies on 0 of the upper scale. So, we
110 100 90 80 70 read the upper scale. QR meets on 102.
50130 61020 m PQR 102
14040
15300 14040 PQR is an obtuse angle.
15300
175
20160 160
20
10 170
170 10
0 180
180 0
PQ
