In a pervious post:
"The equation (x-h)²+(y-k)² = r² describes a circle of radius r centered at the coordinates (h,k) so the circle you have is centered at (2, -4) and has a radius of 3. And, like all circles, the area is given by A = πr² so your circle has an area of 9π = 28.274."
How did they find the radius? Please provide any other additional information on how to work the problem, like step-by-step procedures.
2007-01-31 05:49:15 · 9 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
Like the poster suggested, the single number after the equal sign is the square of the radius (r²). So do the square root of 9 to get the radius.
2007-01-31 05:56:40 · answer #1 · answered by hayharbr 7 · 1⤊ 0⤋
(x+4)^2 + (y-2)^2 = 9 the final variety of the equation of a circle is (x+a)^2 + (y+b)^2 = r^2 the place (-a,-b) is the middle and r is the radius. r^2 = 9 on your challenge so the circle radius is 3. (-a,-b) = (-4,2). This if generally confusing, yet merely set x + 4 equivalent to 0 and sparkling up. Set y-2=0 and sparkling up. in prevalent, set x + a = 0 and y + b = 0 and sparkling up the place a,b are constants.
2016-10-16 09:05:36 · answer #2 · answered by carris 4 · 0⤊ 0⤋
As it says
(x-h)^2+(y-k)^2=r^2
r is the radius
so
(x-2)^2+(y+4)^2=9
h=2; k=-4; and r=sqr(9)
sqr(9)=3
so r=3
radius = 3
Area of a circle = πr²
area = π(3)²
area = π*9
area = 9π or approximately 28.274
2007-01-31 05:57:14 · answer #3 · answered by Bill F 6 · 0⤊ 0⤋
(x-h)²+(y-k)² = r²
(x-2)²+(y-4)² = 3² ( 3*3 = 9)
so when u compare the both h = 2, k = 4 and r = 3
so radius is 3
2007-01-31 06:13:27 · answer #4 · answered by sweetrascal 1 · 0⤊ 0⤋
They found the radius from the standard equation of a circle.
Your equation has the same format.
Matching your equation to the standard, the value of r^2 = 9.
That makes r = sqrt(9) = 3
It's that simple.
2007-01-31 05:57:21 · answer #5 · answered by MamaMia © 7 · 0⤊ 0⤋
How did they find the radius? The answer is in the equation (x-h)²+(y-k)² = r² , where r is the radius. ie r² = 9; r = 3.
2007-01-31 05:56:42 · answer #6 · answered by Kirstin 2 · 1⤊ 0⤋
Equation of circle centre (a,b) and radius r is given by (x - a)² + (y - b)² = r²
In your equation r² = 9
Area = ¶r² = ¶ x 9 = 28.3 ins²
2007-01-31 06:13:15 · answer #7 · answered by Como 7 · 0⤊ 0⤋
9=3*3
so r=3
2007-01-31 05:56:05 · answer #8 · answered by hratanasov 1 · 0⤊ 0⤋
r^2 = 9
the first part (x - 2 )² + (y + 4 )² doesnt matter for area
so r = 3
pi * 3^2 = pi *9 = 28.27
2007-01-31 05:56:51 · answer #9 · answered by Matt S 1 · 1⤊ 0⤋