Parts of a Circle

Every point on a circle is the same distance, the radius, from the centre, and a diameter is two radii end to end: \(d = 2r\). This NSW Year 8 maths subtopic (NESA outcome MA4‑LEN‑C‑01) names the parts of a circle: chord, diameter, arc, sector, segment, quadrant, semicircle and tangent.

You will tell a sector from a segment, see that a diameter is the longest chord, and use equal radii to find lengths and angles in triangles drawn inside a circle. You will divide the circumference of a plate and of a bike wheel by the diameter and find the answer is always close to \(\pi\). You will also work with a metal washer, a clock face in a square frame and circles that touch. It is part of Year 8 Area and Perimeter.