Circles Flashcards
What is the formula for the circumference of a circle?
C=πD
or
C=2πr
What is the formula for the area of a circle?
A=πr2
What is the value of π to 2 decimal places?
3.14
How do you find the arc length?
- Find the circumference of the full circle
- Find the fraction of the circumference by using ‘angle/360’
How do you find the perimeter of a part circle?
- Find the circumference of the full circle
- Find the fraction of the circumference by using ‘angle/360’
- Add the arc length and the two radii together
How do you find the area of a part circle?
Find the area of the full circle
Find the fraction of the area by using
‘angle/360’
How do you find the diameter from a given circumference?
Substitute into the formula
C=πD
and solve
(Divide by π)
How do you find the radius from a given area?
Substitute into the formula
A=πr2
and solve
(Divide by π and then √ )
What are the steps to find the area of the shaded segment?
Calculate:
Area of full circle
Area of sector (quarter circle)
Area of triangle (1/2 base x Height)
Subtract the Triangle from the Sector