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CIRCLE
Prepared by : Pang Kai Yun, Sam Wei Yin,
Ng Huoy Miin, Trace Gew Yee,
Liew Poh Ka, Chong Jia Yi
CIRCLE
A circle is a plain figure enclosed by a curved line, every point on which is equidistant from a point within, called the centre.
DEFINITION
Circumference - The circumference of a circle is the perimeter
Diameter - The diameter of a circle is longest distance across a circle.
Radius - The radius of a circle is the distance from the center of the circle to the outside edge.
EXAMPLE (AREA OF SEGMENT)
Solution:(i) = 8 cm= r θ 8 = r θ 8 = 6 θ θ = 1.333 radiansÐ AOB = 1.333 radians
The above diagram shows a sector of a circle, with centre O and a radius 6 cm. The length of the arc AB is 8 cm. Find(i) Ð AOB(ii) the area of the shaded segment.(ii) the area of the shaded segment (θ - sin θ) (1.333 - sin 1.333) (36)(1.333 – 0.927) 6.498 c
GIVEN THE RADIUS AND DISTANCE TO CENTER
This is a simple application of Pythagoras' Theorem.
Chord length =
EXAMPLE 2
Find the chord of the circle where the radius measurement is about 8 cm that is 6 units from the middle.
Solution:Chord length = = = = = 10.58 cm
PERIMETER OF A SEMICIRCLE Remember that the perimeter is the
distance round the outside. A semicircle has two edges. One is half of a circumference and the other is a diameter
So, the formula for the perimeter of a semicircle is: Perimeter = πr + 2r
AREA OF A SEMICIRCLE
A semicircle is just half of a circle. To find the area of a semicircle we just take half of the area of a circle.
So, the formula for the area of a semicircle is: Area =