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  2. What is the formula for the radius of a semi-circle? - Socratic

    socratic.org/questions/what-is-the-formula-for-the-radius-of-a-semi-circle

    We can solve for r to show an expression for the radius of a semicircle when given the area: A= (pir^2)/2 2A=pir^2 (2A)/pi=r^2 r=sqrt ( (2A)/pi) If given the diameter: The diameter, like in a normal circle, is just twice the radius. 2r=d r=d/2 If given the perimeter: The perimeter of a semicircle will be one half the circumference of its ...

  3. How do I find the radius of a circle from its circumference?

    socratic.org/questions/how-do-i-find-the-radius-of-a-circle-from-its-circumference

    π = 22 7 or 3.142. r = radius. Hence you can find the radius of the circle from the circumference.. C = 2πr. Divide both sides by 2π. C 2π = 2πr 2π. C 2π = 2πr 2π. C 2π = r. r = C 2π.

  4. How do I find the radius of a circle from its general equation?

    socratic.org/questions/how-do-i-find-the-radius-of-a-circle-from-its-general...

    The general form of a circle looks like ... x^2+y^2+Ax+By+C=0 In the standard form to the equation for a circle look like ... (x-h)^2+(y-k)^2=r^2 sqrt(r^2)=r,radius Convert the general form to standard form by using the completing the square process. You will then have the r^2 value. The square root of r^2 is the radius of the circle.

  5. How do you find the radius of a circle if you have the ... -...

    socratic.org/questions/how-do-you-find-the-radius-of-a-circle-if-you-have-the...

    A formula for the circumference of a circle is: C = 2pir Solve the formula for r: r = C/(2pi) Substitute in the given circumference.

  6. Deriving Formulae Related to Circles using Integration

    socratic.org/.../deriving-formulae-related-to-circles-using-integration

    The formulas for circumference, area, and volume of circles and spheres can be explained using integration. By adding up the circumferences, 2\pi r of circles with radius 0 to r, integration yields the area, \pi r^2. The volume of a sphere can be found similarly by finding the integral of y=\sqrt {r^2-x^2} rotated about the x-axis.

  7. The radius of a circle is 6.5. What is the diameter ... -...

    socratic.org/questions/the-radius-of-a-circle-is-6-5-what-is-the-diameter...

    The radius measures 6.5, so we have enough information to solve for A. A = r2 π. A = 6.52 π. A = 42.25π or 132.73. The area is 42.25π units2 or 132.73 units2. Hopefully you understand some of the characteristics of circles now! Answer link. Diameter : 13 Circumference : 13pi Area : 42,25pi The diameter is 2 times the radius so the diameter ...

  8. How do you find the radius of a circle given the length of an...

    socratic.org/questions/how-do-you-find-the-radius-of-a-circle-given-the-length...

    If you have the sector angle θ, and the arc length, l then you can find the radius. r = 180 ×l πθ. Answer link. The circle with radius r has a circumference 2*pi*r which corresponds to an angle of 360^o. If you are given an arc of a certain angle lets say p^o degrees which is l in length then p^o/360^o=l/ (2*pi*r)=>r= (360^o*l)/ (2*pi*p^o)

  9. The area of a circle is 16pi. What is the circumference of ... -...

    socratic.org/questions/the-area-of-a-circle-is-16pi-what-is-the-circumference...

    Answer link. 8pi The area of a circle is pir^2 where r is the radius. So we are given: pir^2 = 16pi Dividing both sides by pi we find r^2=16=4^2 and hence r=4. Then the circumference of a circle is 2pir so in our case: 2pir = 2*pi*4 = 8pi color (white) () Footnote Why is the circumference and area of a circle given by these formulas?

  10. Equation of a Circle - Geometry - Socratic

    socratic.org/geometry/circles/equation-of-a-circle

    A circle C has equation #x^2+y^2-6x+8y-75=0#, and a second circle has a centre at #(15,12)# and radius 10. What are the coordinates of the point where they touch? If a circle has center (0,0) and a point on the circle (-2,-4) write the equation of the circle.?

  11. How do you find the domain and range of a circle? - Socratic

    socratic.org/questions/how-do-you-find-the-domain-and-range-of-a-circle

    The graph is a circle so all the points are enclosed in it. The domain is the values for x so you subtract the radius from the centre coordinate and you add the radius to it. The range is the values for y so you do the same to the y coordinate. If you use (x + 2)2 + (y − 4)2 = 25. The centre is (-2,4) radius is 5. Domain ⇒ − 2 − 5 = − 7.