The formula for the area of a circle is A = πr2, where π is pi, which is 3.14159 rounded to five decimal places, and r is the radius of the circle. Radius is half the diameter of a circle. The radius is a distance measurement, such as meters or feet. Suppose you have a circle with a radius of 0.25ft.
A = πr2 = 3.14159 x (0.25ft)2 = 3.14159 x 0.0625ft2 = 0.19635ft2
If you look carefully, you will see that the radius, a distance measurement, is squared, so the area of a circle will always be a squared distance measurement, such as ft2, in2, m2, cm2, etc... .
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It is its square area which is found by pi*radius squared
to find the area of a semi circle measure the length of the straight edge, divide by 2, square it and multiply by pi. This will give you the area of the circle. To get the area of the semi-circle divide your answer by 2
A circle within a square has a diameter equal to the side of the square = ' D '. Area of the square = D2 Area of the circle = pi R2 = pi (D/2)2 = pi/4 D2 Area inside the square but outside the circle = D2 - (pi/4 D2) = (1 - pi/4) D2 = 0.2146 D2(rounded)
Area of the circle = pi*7.8752 = 194.8278319 square units Area of sector = 75/360 times 194.8278319 = 40.58913165 square units
The radius (in feet) squared times PI (3.14159...)