Question

observation.
Table
I.NO
Radius
Arc
(Major, Minos, semicircle)
measure angle AOB and APB
Observations
You will
completely
fig. 9 (e)
observe
cerer
that two replices
AOB , showing that
of LAPB
LAOB 2 LAPB
This verifies that the angle subtended by an are at
the centre of a circle is twice the angle subtended
by the same are at any other point on the
I remaining part of the circle
Result
Angle subtended by an are at the centre of a
circle is twice the angle subtended by the came acc
at any other point on the remaining part of
the arcle.​

Answer 1

Answer:

Draw a circle of any radius with centre O on a glazed paper. Cut it and paste it on white paper.

Fold the circle along the line passing through the centre O to get a diameter AB.

cbse-class-9-maths-lab-manual-angle-in-a-semicircle-major-segment-minor-segment-1

Take any point P on circumference of the circle.

Join AP and BP by paper folding to get ∠APB.

Make two replicas of ∠APB with the help of tracing paper such that ∠A1P1B1 and ∠A2P2B2.

Place two ∆A1P1B1 and ∆A2P2B2 such that ∠P1 and ∠P2 coincide each other [fig.(ii)].

cbse-class-9-maths-lab-manual-angle-in-a-semicircle-major-segment-minor-segment-2

We notice ∠A1P1B1 and ∠A2P2B2 form a linear pair.

∴ ∠A1P1B1 + ∠A2P2B2 = 180° (linear pair).

2∠APB = 180° (∠A1P1B1 and ∠A2P2B2 are replicas of ∠APB)

∴ ∠APB = 90°