geomotry - equation for a circcle?

Question

what is the general equation of a circle with center at the origin and raduis r? what is the general equation of a circle with center (h,k) and radius r? what is the key to deriving these formulas?

Answer 1

For a circle with center at the origin: x^2 + y^2 = r^2

For a circle with center (h,k) : (x-h)^2 + (y-k)^2 = r^2

Answer 2

For a circle with center at the origin: x^2 + y^2 = r^2

For a circle with center (h,k) : (x-h)^2 + (y-k)^2 = r^2

these formulas were derived using the distance formula, as the distance between any point on the circle and the center is the raduis.

Answer 3

Pie R^2

Answer 4

C= 2pi times r, A= pi times r times r

Answer 5

my teacher taught me this a while ago...(to the toon of twinkle,twinkle little star)



trace your finger round a jar, circumference equals 2 pi r

for area u multiply, r squared times that # pi

twinkle, twinkle little star, knowing math will take u far



hope it helps! i didnt really understand the question though :b

Answer 6

omg im learning that rite now.!

lol.!

the center with (h,k) is this:





[x-h]^2 + [y-k]^2 =r^2

Answer 7

(x-a)^2 + (y-b)^2 = r^2



just replace (h, k) with a and b

h=a, k=b