If the radius of a circle is doubled, what happens to the Area?
549743
Area increases 4 times. Beacause Area of circle = PiR2.\n\nSo if R doubles then radius will be 2R.\n\nHence area will be Pi(2R)2. which results into\n\n4 Pi R2.
829290
2 X pi X  r = cirumference\n\npi X r squared = area
663303
it would be called tangent...if it touches the outside of the circle once.\n\nthe radius of the circle is a line that goes through the cirlce half way, the diamiter is a line that goes through the circle and cuts it right in half, so the radius is half the diamiter.\n\nsecant intersects a cirlce at two points.\n\nSO the answer is tangent.\n\nhope this helps.
415440
r decreases becuase the ellipse is becoming thinner i think that would happen\n\nhope u find out if my answer is wrong GOOD LUCK!!!!!!!!
837293
I haven't done one of these in quite a while. \n\nWhat would you differential element be?  How about r*(dtheta)*dr?\n\nthat sort of a ds*dr   where ds depends on the radius.  Try it! \n\nNote that without the sin theta you'd get the int rdthetadr with r 0 to R and theta 0 to 2pi  You'd get the correct area of a circle.\n\nTry the intergral, see if it makes sense.  Then sketch the figure and estimate it's area to compare.  My confidence is increasing as I write this.
814140
The surface area of a sphere is 4 pi r^2 or 12.57 r^2.\nThe area of a curved surface of a spherical segment of height h, and radius of sphere r is equal to  2 pi r h\nSo, the area a=2 pi r h
471852
Area of a circle = pi*r^2 and the radius is half of the diameter, so 15 feet in this case. (15 feet)*(15 feet)*3.14 = 706.5 feet^2\n\nSo about 706.5 square feet.
303304
Use the well known formulas that relate the radius and diameter of a circle to its circumfrence.\n\nC = pi * D\nC = 2 * pi * R\n\nFor pi, you can use 3.14 or 22/7, or whatever value your teacher wants you to use.
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
826403
hmmm taking me way back here.  when you break the area under a curve into rectangles of differential width,  either the left top corner will lie on the curve or the right top corner will.  \n\nas you decrease the differential width the area will become more exact until bada bing you are doing calculus.  i think.
831242
This is just the inside of the unit circle including its circumference.\nThe unit circle (circle at the origin with radius=1) is\nx^2 + y^2 = 1\nAnd you want x^2 + y^2 ≤ 1\nso its the circle plus its inside.\n( if it had been x^2 + y^2 ≥ 1 it would be the circle plus everything outside )\nIf you wanted x in terms of y, you just get |x| ≤ √(1-y^2) .
927299
It means "2 times pi times r" (where r is the radius of the circle)
937424
Area = pi r^2\nd Area/ dr = 2 pi r\n\nd Area = 2 pi r dr\n\nGiven d Area = 2 dr,  so substitute to get 2 dr = 2 pi r dr\n\n1 = pi r\n\n1/pi = r
568696
rare gem's answer is right..given the radius you'll just need to compute for the area using the formula right?\n\nArea=(radius^2)(pi)\n    = (5)(5)(pi)
799820
the radius is 1/2 the distance across a circle, while the diameter is twice the radius and is a straight line passing through the center of the circle to another side of the circle.
237156
Pi * r^2\n\n(Pi R Squared)\n\nwhere R is the radius (which is also equivalent to half the diameter)
747001
I'm assuming you are familiar with calculus.  Consider an infinitesimal cylinder at height 'y' of thickness 'dy'.  The surface area of that cylinder is 2*pi*Radius*thickness.  Here the radius is simply 3e^2y, and 'dA' the infinitesimal area is given by 2*pi*3e^2y*dy.  To get the total area gotten by rotating this curve, (note we don't have to do any rotation as its already factored in by the assuming an infinitesimal cylinder) simply integrate between 0-3 the above expression, which I leave as an excercise for you.  Hope this helps.