10.1 Circles I
10.1.1 Parts of a Circle
1. A circle is set of points in a plane equidistant from a fixed point.
2. Parts of a circle:
(a) The centre, O, of a circle is a fixed point which is equidistant from all points on the circle.
(b) A sector is the region enclosed by two radii and an arc.
(c) An arc is a part of the circumference of a circle.
(d) A segment is an area enclosed by an arc and a chord.
10.1.2 Circumference of a Circle
Calculate the circumference of a circle with a diameter of 14 cm.
10.1.3 Arc of a Circle
The length of an arc of a circle is proportional to the angle at the centre.
Calculate the length of the minor arc AB of the circle above.
10.1.4 Area of a Circle
Calculate the area of each of the following circles that has
(a) a radius of 7 cm,
(b) a diameter of 10 cm.
10.1.5 Area of a Sector
The area of a sector of a circle is proportional to the angle at the centre.