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SingaporeMathsQuick questions
Geometry and Circle Properties
Quick questions on Angle properties of circles explained: N(A)-Level Mathematics Geometry and Circle Properties
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is parts of a circle?Show answer
A few names you need: the centre is the middle point; a radius joins the centre to the circle; a diameter is a chord through the centre (twice the radius); a chord joins two points on the circle; and a tangent is a line that touches the circle at exactly one point.
What is the angle in a semicircle?Show answer
If a triangle is drawn inside a circle so that one side is a diameter, then the angle at the point on the circle (opposite the diameter) is a right angle:
What is two radii form an isosceles triangle?Show answer
Because all radii of a circle are equal, a triangle with two sides that are radii is isosceles. Its two base angles (opposite the equal radii) are therefore equal. This often supplies an extra equal angle in a circle problem.
What is combining with the angle sum?Show answer
Most circle questions use one property to find a right angle or an equal angle, then finish with the triangle angle sum of . Work one step at a time, naming each property.
What is not using equal radii?Show answer
Two radii make an isosceles triangle with equal base angles - an easy extra fact to forget.
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