Circle Theorems: Edexcel 4MA1 Past Paper Questions and Worked Solutions
This page collects every circle theorems question from the Pearson Edexcel International GCSE Mathematics A (4MA1) Higher tier Paper 1H and Paper 1HR, January 2020 to June 2025: 9 questions worth 37 marks. Questions run from easier to harder. Try each one first, then click “Show solution” for a step-by-step method with the reason for every step. All answers are checked against the official Pearson mark schemes.
A, B, C and D are points on a circle, centre O. Angle BCD = 128°. Work out the size of angle OBD. Give a reason for each stage of your working.
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- ABCD is a cyclic quadrilateral, so opposite angles add to 180°: angle BAD = 180° − 128° = 52° (opposite angles of a cyclic quadrilateral add up to 180°).
- Angle BOD = 2 × 52° = 104° (the angle at the centre is twice the angle at the circumference).
- OB = OD because both are radii, so triangle OBD is isosceles (base angles of an isosceles triangle are equal).
- Angle OBD = (180° − 104°) ÷ 2 = 76° ÷ 2 (angles in a triangle add up to 180°)
Answer: 38°
A, B and C are points on a circle, centre O. Angle ABC = 38°. Work out the size of angle OAC. Give a reason for each stage of your working.
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- Angle AOC = 2 × 38° = 76° (the angle at the centre is twice the angle at the circumference).
- OA = OC (radii), so triangle OAC is isosceles (base angles of an isosceles triangle are equal).
- Angle OAC = (180° − 76°) ÷ 2 (angles in a triangle add up to 180°)
Answer: 52°
B, D, E and F are points on a circle. ABC is the tangent at B to the circle. Angle ABD = 39° and angle EFD = 18°. Work out the size of angle BDE. Give reasons for your working.
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- Angle BFD = angle ABD = 39° (alternate segment theorem: the angle between the tangent and chord BD equals the angle in the alternate segment).
- Angle BFE = angle BFD + angle DFE = 39° + 18° = 57°
- BDEF is a cyclic quadrilateral, so angle BDE = 180° − 57° (opposite angles of a cyclic quadrilateral add up to 180°)
Answer: 123°
A, B, C and D are points on a circle, centre O. AOC is a diameter of the circle. Angle BAC = 55°. Work out the size of angle ADB. Give a reason for each stage of your working.
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- Angle ABC = 90° (the angle in a semicircle is 90°, because AC is a diameter).
- Angle ACB = 180° − 90° − 55° = 35° (angles in a triangle add up to 180°).
- Angle ADB = angle ACB (angles in the same segment are equal: both stand on the chord AB).
Answer: 35°
B, D, E and F are points on a circle. ABC is the tangent to the circle at B. Angle EDF = 40° and angle FBC = 70°. Prove that the tangent ABC is parallel to EF. Give a reason for each stage of your working.
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- Angle EBF = angle EDF = 40° (angles in the same segment are equal: both are subtended by the chord EF). [Join BE to see this angle.]
- Angle BEF = angle FBC = 70° (alternate segment theorem).
- In triangle BEF: angle BFE = 180° − 40° − 70° = 70° (angles in a triangle add up to 180°).
- So angle BFE = angle FBC = 70°. These are alternate angles between the lines EF and ABC, with BF crossing them.
Answer: Alternate angles BFE and FBC are both 70°, so ABC is parallel to EF
P, Q and R are points on a circle, centre O. TRV is the tangent to the circle at R. Reflex angle POR = 238°. Angle QRV = 60°. Calculate the size of angle OPQ. Give a reason for each stage of your working.
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- Angle POR = 360° − 238° = 122° (angles around a point add up to 360°).
- OP = OR (radii), so triangle OPR is isosceles: angle OPR = (180° − 122°) ÷ 2 = 29° (base angles of an isosceles triangle are equal; angles in a triangle add to 180°).
- Angle QPR = angle QRV = 60° (alternate segment theorem: the angle between a tangent and a chord equals the angle in the alternate segment).
- Angle OPQ = angle QPR − angle OPR = 60° − 29°
Answer: 31°
P, Q, R and S are points on a circle with centre O. PS is a diameter of the circle. Angle PQR = 136°. Work out the size of angle RPS.
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- PQRS is a cyclic quadrilateral, so opposite angles add up to 180°: angle PSR = 180° − 136° = 44°
- PS is a diameter, so angle PRS = 90° (the angle in a semicircle is 90°).
- Angles in triangle PRS add up to 180°: angle RPS = 180° − 90° − 44°
Answer: 46°
L, M, N and P are points on a circle, centre O. Angle MNP = 58°.
(a)(i) Find the size of angle MLP. (ii) Give a reason for your answer. (2)
(b) Find the size of the reflex angle MOP. (2)
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Part (a)
- LMNP is a cyclic quadrilateral and angle MLP is opposite angle MNP.
- 180° − 58° = 122°
Answer: 122°, because opposite angles of a cyclic quadrilateral add up to 180°
Part (b)
- The angle at the centre is twice the angle at the circumference: angle MOP = 2 × 58° = 116°
- Reflex angle MOP = 360° − 116°
Answer: 244°
PTR and QTS are chords of a circle that cross at T. PT = (3y − 5) cm, QT = (y + 3) cm, RT = 4x cm and ST = (x + 2) cm. Find an expression for y in terms of x.
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- Intersecting chords theorem: when two chords cross, PT × TR = QT × TS.
- (3y − 5) × 4x = (y + 3)(x + 2)
- Expand both sides: 12xy − 20x = xy + 2y + 3x + 6
- Collect the y terms on one side: 12xy − xy − 2y = 3x + 6 + 20x, so 11xy − 2y = 23x + 6
- Factorise out y: y(11x − 2) = 23x + 6
Answer: y = 23x + 611x − 2
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