Page 72 - Key Stage 3 Geometry

angle subtended by the chords and B is the angle

subtended by the radii. A = 2B. You are now to show
this is true.

Exercise 5.1
1. Draw a circle of radius 5 cm and mark the centre

with a dot.

2. Draw two radii as shown in the circle on the
previous page.

3. Draw two chords from the ends of the radii to a

point on the circumference. Mark the point they
meet with a dot.

4. Mark your two angles A and B.

5. Using your protractor on one of the radii with
the dot under the cross-hairs and then measure

angle A.
6. Place your protractor alone one of the chords

with the circumference dot under the cross hairs

and measure the angle B.
7. Confirm that A = 2B.

Whenever a triangle is formed from two radii, it is

worth noting it will always be an isosceles triangle –

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