Checkpoint: parts, chords and the doubling

Two radii and one arc cut off a piece of a circle. What is it called?

• A sector, since it has two radii and an arc
• A segment, since it is a piece of the disc
• A chord, since two straight edges bound it

A circle has radius 15 cm and a chord 24 cm long. How far is that chord from the centre?

• 12 cm, which is half the chord
• 9 cm, since 225 − 144 = 81
• 3 cm, from 15 take away 12

Two chords sit 6 cm and 9 cm from a circle's centre. Which is true?

• The one 6 cm out is longer, since it is nearer
• Neither, since the lengths are not given
• 9 cm out is longer, since 9 is more than 6

An arc makes an angle of 130° at the centre. What angle does it make at the rim?

• It depends on which point of the rim you choose
• 260°, since the edge angle is the bigger one
• 65°, since 130 ÷ 2 = 65

P and Q both sit on chord AB's major arc. What can you say about angles APB and AQB?

• The one nearer the chord is the bigger one
• They are equal, whatever P and Q are
• They add up to 180°