Q&A for How to Calculate the Radius of a Circle

It is possible to have quite a few circles, all with different radii, in which one could draw a chord of a given, fixed length. Hence, the chord length by itself cannot determine the radius of the circle.

Divide the central angle into 360°. Multiply the resulting number by the arc length. That gives you the circumference of the circle. Divide the circumference by pi. That's the diameter. Half of the diameter is the radius of the circle.

Technically you can't "calculate" the radius in such a situation. However, it is possible, by construction, to locate the center of such a circle, and then, simply by physically measuring, determine the radius. To do the construction, draw any two chords and construct their perpendicular bisectors; their point of intersection is the center of the circle. Then draw in any radius and measure it with a ruler. Not technically a "calculation."

STEP 1 : radius = D/2. 11/2 = 5.5 STEP 2 : circumference = 2 x pi x r = (2)(pi)( 5.5) = 11 x pi = 34.54 STEP 3 : area = pi x r^2 = pi (5.5 * 5.5 ) = 30.25 x pi = 94.99

Figure out the ratio of the length of the arc to the circumference and set it equal to the ratio of the measure of the arc (shown with a variable) and the measure of the entire circle (360 degrees). For example: If the circumference of the circle is 4 and the length of the arc is 1, the proportion would be 4/1 = 360/x and x would equal 90.

Take the square root of the area of the circle and divide by pi.

The area of a circle is equal to pi times the radius squared.

The circumference is equal to the radius multiplied by 2pi. Given the circumference, divide the circumference by 2pi and that's your radius. In this case, your radius should be around .28.

By using the formula C = 2* pi * r =(2)(3.141)(4.75) = 29.84 cm

You can't do it without additional information.

A = πr² (r is the radius). It's given that A = 5C (where C is the circumference). (C=πd) (d is the diameter). Therefore, A = πr² = 5C = 5πd = 5π(2r) = 10πr. Thus, πr² = 10πr. Solve for r by dividing both sides of that last equation by πr.

Use the formula for the volume of a cylinder, which is V = (pi)(r^2)(h). Plug in the values of the volume (V) and height (h). Then, solve for r.

If you know the two endpoints of the radius, you can use the distance formula to calculate the length. Read the following article for more information: https://www.wikihow.com/Use-Distance-Formula-to-Find-the-Length-of-a-Line

If you know the length and the central angle of the arc, first find what fraction of the full circle is represented by the arc. For example, if the central angle is 40°, that's 40/360 of the full circle, which reduces to 1/9 of the circle. Then multiply the length of the arc by (in this case) 9. So if the length of the arc is 7 cm, the full circumference is 7 cm multiplied by 9, or 63 cm.

See Round Numbers .

Calculate the area. First find the semiperimeter of the triangle (add the sides and halve this result), then substitute this result as s and the side lengths as a, b and c in the formula A = (s(s-a)(s-b)(s-c))^0.5 . Make sure your calculations are correct! Now, divide the area by the semiperimeter to get the radius. So r = ((s(s-a)(s-b)(s-c))^0.5) / s .

You don't have enough information to find the radius.

Assuming the tank is 1.3 m in diameter, the circumference is πd, or (3.14)(1.3) = 4.08 meters.

If you have the radius of the circle, then the formula would be C = 2πr (or C = 2 x π x r). Or if you have the diameter, the formula would be C = dπ (or C = d x π).

Use Method 2 above.

Find the radius by using the volume. The radius equals the cube root of the following quantity: three times the volume, divided by 4π.

If you have half the circumference, multiply it by two to get the whole circumference. Then use the formula of circumference = pi X diameter to get a different version of that in order to find the diameter. In this case the version would be diameter = pi / by circumference. So now you have the diameter. Simply half that to get the radius.

3 centimeters. The radius is always half of the diameter.

A circle is a 2-D object, and has no mass.

Area= pi r 2 (Apple pies are too). Square the radius and times the result by pi. You will then get the area. It is best to do it with a calculator.

Theoretically, a tangent has unlimited length.

It's easiest to show this by example. Let's say the difference between the circumference and the diameter is 3 inches. So C - d = 3, and C = d + 3. Then C = πd = 3.14 d = d + 3. Then 3.14 d - d = 3. That means 2.14 d = 3, and d = 3 / 2.14 = 1.4. The radius is 1.4 / 2 = 0.7 inch. [Look at that middle step this way: (3.14)d - (1)d = (2.14)d = 3.]

If you mean that you are given the length of one-quarter of the circle's circumference, multiply that by 2 (to get half the circumference), and divide by pi to get the radius.

Assuming the angle given is the central angle of the sector, multiply the area of the sector by 360° and divide by the central angle. That gives the area of the full circle. Divide that by pi, and then find the square root of that quotient. That's the radius.

If r = 2.59, r² equals slightly more than 6.69.