Download presentation
Presentation is loading. Please wait.
Published byWilla Lewis Modified over 8 years ago
2
Circles…… Area and Circumference
3
The Circumference of a Circle Find the circumference of the following circles. C = d C = 2 r 8 cm 1 9.5 cm 2 C = d C= x 8 C = 25.1 cm (1 dp) C = d C= x 9.5 C = 29.8 cm (1 dp)
4
C = 2 r C = 2 x x 3 C = 18.8 mm (1 dp) C = 2 r C = 2 x x 2.1 C = 13.2 m (1 dp) The Circumference of a Circle Find the circumference of the following circles. C = d C = 2 r 3 mm 4 2.1 m 3
5
The Circumference of a Circle Find the perimeter of the following semi-circles. C = d C = 2 r 8 cm 1 9.5 cm 2 Perimeter = ½ d + d = ½ x x 8 + 8 = 20.6 cm (1 dp) Perimeter = ½ d + d = ½ x x 9.5 + 9.5 = 24.4 cm (1 dp)
6
Perimeter = ¼ ( 2 r) + 2r = ¼ x 2 x x 6 + 2 x 6 = 21.4 cm (1 dp) Perimeter = ¾(2 r) + 2r = ¾ x 2 x x 8.5 + 2 x 8.5 = 57.1 cm (1 dp) The Circumference of a Circle Find the perimeter of the ¼ and ¾ circles. C = d C = 2 r 3 4 6 cm 8.5 cm
7
A = r 2 A = x 8 2 A = 201.1 cm 2 (1 dp) A = r 2 A = x 9.5 2 A = 283.5 cm 2 (1 dp) The Area of a Circle Find the area of the following circles. A = r 2 8 cm 1 9.5 cm 2
8
The Area of a Circle Find the area of the following circles. 6 mm 3 2.4 m 4 A = r 2 A = x 3 2 A = 28.3 mm 2 (1 dp) A = r 2 A = x 1.2 2 A = 4.5 m 2 (1 dp) A = r 2
9
The Area of a Circle Find the area of the following semi-circles. 8 cm 1 9.5 cm 2 A = ½ r 2 = ½ x x 4 2 = 25.1 cm 2 (1 dp) A = ½ r 2 = ½ x x 4.75 2 = 35.4 cm 2 (1 dp) A = r 2
10
A = ¼ r 2 = ¼ x x 6 2 = 28.3 cm 2 (1 dp) A = ¾ r 2 = ¾ x x 8.5 2 = 170.2 cm 2 (1 dp) The Area of a Circle Find the area of the ¼ and ¾ circles. 3 4 6 cm 8.5 cm A = r 2
11
r 2 = 25 r 2 = 25/ r = (25/ ) r = 2.82 d = 2 x 2.82 = 5.6 cm 1dp A = r 2 The Area of a Circle Find the radius/diameter of the following circles. A = 25 cm 2 find the diameter. 6 5 A = 30 cm 2 find the radius. r 2 = 30 r 2 = 30/ r = (30/ ) r = 3.1 cm 1dp
12
ARCS and SECTORS of CIRCLES Sector O A B The angle between two radii of a circle divides the circle into a minor and a major sector. The arc lengths of each sector are the minor and major arcs respectively. Arc
13
Example Question: The shape below is a sector of a circle of radius 8.4 cm. Find (a) the arc length and (b) sector area. 100 o 8.4 cm 160 o 3.1 m Now try this one.
Similar presentations
© 2024 SlidePlayer.com. Inc.
All rights reserved.