What is the formula to get the area of a circle?
480203
Area of a circle = pi*r^2\n\nr=radius os the circle
589996
Assuming that A, B, C are all on the same line.\n\nLarger circle:\nRadius = AC = 6\nArea = PI * r^2 = 36*PI\n\nSmaller circle:\nRadius = AC - AB = 6 - 2 = 4\nArea = PI * r^2 = 16*PI\n\nShaded area:\nArea = (Large A) - (Small A)\n     =  36*PI - 16*PI = 20*PI = 62.8 units^2
554627
the circumference of a circle can be calculated by using the formula:\n circumference of circle=2*pie*r\n where pie=22/7;it is equal to 3.1415;\n r=radius of the circle.\nThanks.
1174230
I think you have to know how many degrees the segment is.  Then, calculate the area of the entire circle:\n\nPI x radius ^ 2 (squared)\n\nThen, divide the degrees in the segment by 360, so if your segment is 54 degrees, it's:\n\n54/360 = .15\n\nThen, multiply the result of the 2nd calculation (.15 in the example) by the area of the circle you calculated in step 1, and there's your answer.\n\nThere's probably a more elegant way, but it's been 25 years since I took a trigonometry or algebra course.
877943
volume of cyllinder = area of circle times height\n\n= Pi x radius x radius  x height\n\nremember its just the same as finding the volume of any prism.\nfind the area of the shape of the end then multiply by its length!!
1127924
Area of rectangle = length x width \nArea of a circle = pi x R x R = pi R^2 where pi~3.14 and R - radius\nArea of an ellipse = pi x a x b see http://www.tpub.com/content/engineering/14069/css/14069_33.htm \n\nVolume = area of the base times hight\nVolume of a rectangular prism= area of rectangle x height = length x width x height\nVolume of a sphere = (4/3)pi x R x R x R = (4/3)pi x R^3\n \nCheck math tables or the web for equation of other geometric figures \n\nPercentage = 100 x (partial amount) / (total amount)\n\nHave fun
999585
I knew it as I did the activity.Draw a circle an divide it into 8 equal parts.It should be equal.Then cut it and stick such that the tip of one cone is up and the other is down.See that the edges stick each other close together.Do it until you finish all the 8 parts.\nNow you needed some concentration.You can see that it forms a parallelogram.Now area of parallelogram=base*height and the circumference of circle=Pi*2*radius.The base of the diagram is half the circumference that is Pi*radius,and the height will be the radius.You will also notice that Area of parallelogram=Area of circle.Therefore,Base*height=Pi *Radius *radius.so, now you have got pi*radius square.\nHope you like my answer.
71760
area := Πr2\ncircumference := Πd  ,  r=radius, d=diameter, Π=3.14128....
572270
triangle area = 1/2(height * width)\n\ncircle area = pi * radius^2
72316
The area of circle is pi*r^2 (pi r square). Now let the increased radius be R and iniitial radius be r.\nArea after expansion  =pi*R^2 (pi R square)\nArea before expansion =pi*r^2 (pi r square)\nIncrease in area      =pi*R^2  - pi*r^2\n                      =pi(R^2 - r^2) \n                      =pi(R+r)(R-r)\n                      =3*(7+5)(7-5), taking pi=3 aprox.\n                      =3x12x2\n                      =72 approx.\n Since answer c alone is near to this value the answer is C.\n\nThough the steps given are more the problem is done mentaly and not by writing these steps. The steps in mental calculations are \n1. 7+5=12\n2. 7-5=2\n3. 3x12x2=72 and choose the answer.
53953
Area of a circle is pi times radius square.\n\nPi is 22/7 and radius is 2 squared\nA=22/7*2^2\nA=22/7*4\nAis apprx. 12.57
234883
The symbol p is called pi and is approximately equal to 22/7 or 3.141592654 , most high school teachers use it to two decimal places as 3.14\np is the ratio between the circumference and the diameter of a circle ..i.e \np = (circumference / diameter ).\nInterestingly the value of p is the same for any circle ... \n\nArea of circle = p x ( radius x radius ) = p radius2\n\nif the Radius = R \nthen \nArea of circle = pR2 = p x R x R \n\nHere's an example:\nFind the area of the circle with radius 10 cm ..use p as 3.14\nAnswer\nHere we have :\nRadius = 10 cm\np = 3.14\n\nUsing the formula Area of circle = p radius2 = p x radius x radius \n\nreplacing radius with 10 cm and p with 3.14 in above formula we have\n\nArea of circle = p radius2 = p x radius x radius = 3.14 x 10cm x 10cm = 3.14 x 100 cm2 = 314 cm2
137325
This is a lot to ask here. Why dont you look it up? \n\nAnd a lot of these are easy to figure out. \n\nSphere surface area is A=4 *pi *R^2 where R is the radius\n\nbecause A={int 0 to 2 pi} {int 0 t0 pi} R^2 sin(a)dadb\n\n\nThe cube surface area is A=6*S^2, where S is the length of an edge because there are 6 sides, each of area A^2.\n\nThe cylinder surface area A=2*pi*(R^2)+2*pi*R*H, where R is radius and H is height, because it has two circular end caps of area pi*(R^2) and a side of dimensions 2*pi*R by H, when it is unrolled. \n\nCone surface areas can be found the same way. Just unroll the side, and you get a triangle with height sqrt(H^2+R^2) and base 2*pi*R. The area of a triangle is .5*base*height. Then add in the area of the round bottom. \n\nAnd so on. I am sure you can do this yourself.
1150077
Any length greater or equal the circumference of a 1-acre circle. \n\nCalculate the acre as square feet, square yards or square meters.\n\nDivide by pi and calculate the square root to get the radius, then multiply by 2 pi for the circle circumference.
586782
The area of segment of a circle is given by\nA = r^2[theta - sin(theta)]/2\n\ntheta is given by\ntheta = 2 arcsin(c/[2r])\n\nwhere c is the chord length and r is the radius.  So,\ntheta = 2 arcsin(c/[2r])\n= 2 arcsin(20/[2(12)])\n= 1.97 radians\n\nSo the area then is\nA = r^2[theta - sin(theta)]/2\n= (12)^2[1.97 - sin(1.97)]/2\n= 75.5 m^2\n\nEDIT:  My answer is indeed correct.  greatindiangenius's angle below is wrong.  You can find that angle theta another way besides the way listed on the link below - if you imagine a triangle formed by the chord and two radii, and if you drop a height from the center to the chord, then you have two triangles with long leg 10 and hypotenuse 12.  The angle between the height and the radius is arcsin(10/12) = 56.44, so the entire angle is 112.88 degrees, or 1.97 radians, not 100.\n\nRecall that a _sector_ is the pie wedge shape of a circle, starting from the center.  But a _segment_ is only the part between the chord and the circle - the ice cream part of the cone, if you break the _sector_ down like that.  So the formula in my reference and my work is correct in that we are finding the area of the ice cream only, and not the ice cream and cone.\n\nWe can find the area of the segment another way: we can take the area of the sector and subtract the are of the triangle formed by the radii and chord.\n\nFor the area of the _sector_, recall that it's just a fraction of the entire area, based on that angle 112.88:\n\nArea of sector = (112.88/360)(pi*12^2)\n= 141.85 m^2\n\nFor the area of the triangle, we need the height (we already have the base, 20).  We can use the Pythagorean theorem:\n\nc^2 = a^2 + b^2\n12^2 = 10^2 + b^2\n144 = 100 + b^2\nb^2 = 44\nb = 2sqrt(11)\n~ 6.63 m\n\nArea of triangle = (1/2)bh\n= (1/2)(20)(6.63)\n= 66.3 m^2\n\nArea of segment = Area of sector - Area of triangle\n= 141.85 - 66.3\n= 75.5 m^2\n\nwhich is the same thing as above with the other formula.
729233
limit is not specified so we asume whole area\n\nx^2+y^2 = a^2\n\nthis is a circle of radius a\n\nso area = pi*a^2
860968
u can use the following formulas to find the radius\n1)Area of circle=pi.*(radius)^2\nwhen area is given plug in that value into this formula and u can get the radius\n2)radius=diameter/2\nwhen the diameter is given,find the radius by dividing the diameter by 2\n3)circumference=2*pi.*r\nwhen the circumference is given use the above formula to solve for the radius\n\nthere is no definite formula for the radius but depending the other value given u can solve for the radius.\nhope that helps!!!