Terminology
distance from the centre to the edge of a circle
Radius
10 cm
Circumference means the perimeter of a circle
TRUE or FALSE
TRUE
what is θ?
"theta", number of degrees
A quadrant is half of a circle
TRUE or FALSE
FALSE
A quadrant is a quater of a circle
distance across the centre of a circle
diameter
Given the radius of a circle is 2.5 cm, what is its diameter?
5 cm
what is the formula to find circumference, C ?
C = 2πr
The arc length of a full circle is just its circumference
TRUE or FALSE
TRUE
The arc length of a full circle is also just its perimeter
Given circumference, C = 2πr
what is formula to find the arc length, L of a semicircle?
(Hint: semircle means half of a circle)
arc length of a semicircle = 1/2 x 2πr
= πr
distance around the circle
circumference
Given the diameter of a circle is 11 cm, what is its radius?
5.5 cm
C = πd
TRUE or FALSE
TRUE
C = 2πr
C = πd
What is the arc length formula?
arc length, L = θ/360° x 2πr
Given circumference, C = 2πr
What is formula to find the perimeter, P of a quadrant?
(Hint: A quadrant means a quater of a circle)
arc length of a quadrant = 1/4 x 2πr
= 1/2 πr
Perimeter of a quadrant = 1/2 πr + r + r
= 1/2 πr + 2r
an area of a circle 'cut of' by a chord
segment
Given the radius of a circle is 40 mm, what is its diameter?
80 mm
Calculate the circumference of a circle with radius 7 cm
C = 2πr
= 2 x π x 7
= 44 cm
Find the arc length of a sector with radius 10 cm and 50° in two decimal places
L = θ/360° x 2πr
= 50/360 x 2 x π x 10
= 8.73 cm
Find the perimeter of a semicircle with radius 10 cm in two decimal places
(Hint: C = 2πr)
Arc length of semicircle = 1/2 x 2πr
= πr
= π x 10
= 31.42 cm
Perimeter of semicircle = 31.42 + 10 + 10
= 41.42 cm
a portion of a circle enclosed by two radii and an arc
sector
What is the formula for finding diameter, d?
d = 2r
Calculate the circumference of a circle with diameter 35 cm, correct to two decimal places
C = πd
= π x 35
= 109.96 cm
Find the perimeter of a sector with 5 m radius and 300° in two decimal places
arc length, L = θ/360° x 2πr
= 300/360 x 2 x π x 5
= 26.18 m
perimeter, P = 26.18 + 5 + 5
= 36.18 m
Find the perimeter of a quadrant with diameter 20 m in two decimal places
(Hint: C = 2πr)
Radius, r = 20/2
= 10 m
arc length of a quadrant = 1/4 x 2πr
= 1/2 πr
= 1/2 x π x 10
= 15.71 m
Perimeter of a quadrant = 15.71 + 10 + 10
= 25.71 m