A circle has a radius of 13 cm with a chord 12 cm away from
MATHEMATICS
JAMB 2023
A circle has a radius of 13 cm with a chord 12 cm away from the centre of the circle. Calculate the length of the chord.
- A. 16 cm
- B. 8 cm
- C. 5 cm
- D. 10 cm
Correct Answer: D. 10 cm
Explanation
|AP| = |PB| = \(x\) (The perpendicular to a chord bisects the chord if drawn from the center of the circle.)
From ?OPB
Using Pythagoras theorem
⇒ \(13^2 = 12^2 + x^2\)
⇒ \(169 = 144 + x^2\)
⇒ \(169 - 144 = x^2\)
⇒ \(x^2 = 25\)
⇒ \(x = \sqrt25 = 5 cm\)
∴ Length of the chord |AB| = \(x + x = 5 + 5 = 10 cm\)
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