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Q: Find the radius for a circle with the equation x2 plus y2 equals 9?

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Area of a circle equals pi (~3.14) multiplied by the radius squared. So to find the area of that circle your equation is (3.14)(3)^2 which equals approximately 27.

The inner circle is x2 + y2 = 4. The radius of the inner circle is the square root of 4, which is 2. To find the radius of the outer circle, multiply 2 times 4. The radius of the outer circle is 8. Square 8 (82 or 8 x 8) to find the number to put into the equation of the outer circle. This is 64. The equation for the outer circle is x2 + y2 = 64.

OK, SO to find the area of a circle, you find the radius (half of the diameter), and fit it into the equation πr2=A where r equals radius and A = area. The perimeter of a circle is π multiplied by the diameter. π is ≈ 3.1415296.

x2 +y2 = R2 =16 = radius 2 R = 4

x^2 + y^2 = r^2

The centre is (3,-1) and the radius is sqrt(10).

The circumference of a circle equals 2 times pi times the radius, in this case, about 31.42 inches.

Half the square root of the square radius equals the circle radius.

Area of a circle equals pi r2 Therefore the radius of a circle equals the square root of (area divided by pi).

If the circumstance of a circle is 108pi then what is the radius of the circle

The general equation for the area of a circle is π*r2, where r is the radius of the circle, and π is pi, which is approximately 3.14159. The diameter of a circle is how far it is from one side of the circle to the other, and the radius is how far it is the from edge to the center, thus the radius is half the diameter. Therefore the area is π*(92) ~ 254.47

A circle with the radius of 21cm would have an area of approximately 1384.74 cm. You would find this by using the equation of pi*(radius^2) = pi*(21^2).

you cant: pi is the same for any circle - 3.1415... the diamter or the radius has to be given diameter divided by two equals the radius the radius times two equals the diameter

To find the circumference of a circle the equation would be pi multiplied by diameter, or radius squared. the answer would be 31.415 units squared.

The equation for the circumference of a circle is 2 multiplied by 3.14 (pi) multiplied by the radius. Since the radius is half of the diameter, it can also be calculated by multiplying the diameter by 3.14.

Area = Pi(radius)squared. You only need the radius of a circle to find the area. To find the radius, when you have the diameter, divide the diameter by 2, because the diameter forms two radii. After you have found the radius, plug in the radius into the area equation: Area = Pi(radius)squared In other words, you can say the other equation for the area of a circle is: Area = Pi(1/2Diameter)squared

Circumference = 2*Ï€*radius = 20*Ï€ feet

The area of a circle equals pi times the radius squared (A = pi*radius2) where pi is 3.1416 So the radius is the square root of the area divided by 3.1416

The equation for finding the circumference of a circle is diameter times pi so reverse it to circumference divided by pi which leaves the diameter. The diameter is twice as big as the radius so divide the diameter by 2 and you will find the radius.

circumference of a circle = diameter*pi or 2*pi*radius

π×(radius)2http:/www.mathwarehouse.com/geometry/circle/area-of-circle.php

Area of the circle in square inches = pi*82

Area of a circle = 3.14 * r2 Thus, radius, r = root of ( Area of a circle / 3.14 ) --------- equation 1 Circumference of circle = 2 * 3.14 * r Therefore, from (equation 1), Circumference = 2 * 3.14 * root of ( Area of a circle / 3.14 ). In a nutshell, first find the radius and then the circumference.

multiple the diameter by 2 to get the radius, then use your equation and go from there

The unit circle is a circle that can be used to find trigonometric functions. The equation of the unit circle is x^2 + y^2 = 1. So it is any circle with radius 1.