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Circle Theorems and Tangents — Free MYP4 Mathematics (Extended) Practice Questions
1QuestionAngles at the Centre and in the CircleConcept Practice
2 marks~3 minCriterion A
A telecommunications engineer is positioning a signal repeater at point C on the boundary of a circular coverage zone. The transmitter and receiver are fixed at points A and B on the boundary, with the network hub at centre O. The engineer knows that ∠ACB=35°.
a
Deduce the measure of ∠AOB. [1]
b
The hub O can only relay signals when the central angle ∠AOB is strictly less than 75°. Justify whether this network configuration meets the relay condition. [1]
Solutions
2QuestionAngles in the Same Segment and Alternate Segment TheoremAssessment Practice
5 marks~8 minCriterion C
Points A, B, C, D, and E lie on the circumference of a circle with centre O. The line segment AE is a diameter. Angle BAC=34°. A surveying team uses this circular arrangement to model sight-lines between observation posts, where a 90° angle between lines confirms a perpendicular alignment required for accurate triangulation.
a
Deduce the measure of angle BCE. [1]
b
Calculate angle BEC and justify which circle theorem you used. [2]
c
Angle EDC is claimed to equal angle BAC. Justify whether this claim is correct, and explain what this means for the sight-lines from posts D and A to the arc EC. [2]
Solutions
3QuestionAngles in the Same Segment and Alternate Segment TheoremAssessment Practice
5 marks~8 minCriterion B
A satellite dish is mounted on a curved support. An engineer models a cross-section of the support as a circle with centre O. A tangent PT touches the circle at point A, and point B lies on the circumference. The angle BAP=θ.
a
State the size of angle OAP, justifying your answer with the appropriate theorem. [1]
b
Prove that triangle OAB is isosceles and hence deduce angle OAB in terms of θ. [2]
c
Prove that ∠AOB=2θ, then advise the engineer whether measuring the tangent angle θ at the mounting point A is a sufficient method for determining the central angle of the support. [2]
Solutions
4QuestionAngles in the Same Segment and Alternate Segment TheoremAssessment Practice
6 marks~9 minCriterion D
A ship's captain navigates between two coastal landmarks, A and B, avoiding a submerged reef. By measuring the angle θ subtended by chord AB from the ship's position, the captain uses the angles in the same segment theorem to stay on a safe circular arc that keeps the reef outside it.
a
Explain how the angles in the same segment theorem guarantees that a constant angle θ keeps the ship on the same circular arc through A and B. [2]
b
Explain two limitations of using angle measurements alone to maintain this safe arc in practice. [2]
c
Advise the captain whether this geometric method alone is sufficient for safe navigation, and justify your advice by recommending at least two specific additional tools or strategies that should be used. [2]