Corollary 4: If the angle standing on a chord at some point of a circle is a right angle, then the chord is a diameter.
Worked example 4
State if the red line in each of the following is (a) a chord and a diameter or (b) just a chord. Justify your answer by stating the axiom, theorem or corollary used. (i)
(i) (i) (ii) (i) (ii) (ii) (iii) (ii) (iii) (iii) (iv) (iii) (iv) (iv) (iv)
89° Solution (ii)
89°
89°
89°
Practice questions 29.2
1. Choosing from the following words, name the labelled parts of the circle shown: segment, sector, chord, circumference, centre, radius, diameter, arc.
(i) C (ii) 2 5 1
3 4
2. Name the angle that is standing on the arc AB in each of the following diagrams.
E 6 7 8
4. A circle with centre O has points A , B and C on the circumference. If |∠ABC| = 22° , fi nd the size of |∠BAC| .
5. In the diagram shown, AB is a diameter of a circle, centre O . C is a point on the circumference of the circle, such that |∠CAB| = 28°.
B A A B
3. For each of the following diagrams, name the arc that ∠MNO is standing on. (i)
(i) O N M N Section C Applying our skills 463 (ii) (ii) M O What is the size of ∠CBA ?
6. On the right is a circle with centre O . AC is a diameter of the circle and B is a point on the circumference. What is the size of angle CBA ?