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  1. Home
  2. 12th grade
  3. Geometry
  4. Exercise : Graph a circle from its equation

Graph a circle from its equation Geometry

Determine the graph of the circles given by the following equations.

\left(x-2\right)^2+\left(y-1\right)^2=4

The standard form of a circle is:

\left(x-h\right)^2 + \left(y-k\right)^2 = r^2

The center of the circle is the point \left(h,k\right) and the radius is r.

Here, the equation is:

\left(x-2\right)^2+\left(y-1\right)^2=4

Therefore:

  • h=2
  • k=1
  • r=2

This is the equation of a circle whose center is \left(2{,}1\right) and radius is 2. We can graph this circle as follows:

-

\left(x-3\right)^2+\left(y+1\right)^2=4

The standard form of a circle is:

\left(x-h\right)^2 + \left(y-k\right)^2 = r^2

The center of the circle is the point \left(h,k\right) and the radius is r.

Here, the equation is:

\left(x-3\right)^2+\left(y+1\right)^2=4

Therefore:

  • h=3
  • k=-1
  • r=2

This is the equation of a circle whose center is \left(3,-1\right) and radius is 2. We can graph this circle as follows:

-

\left(x+1\right)^2+\left(y-1\right)^2=9

The standard form of a circle is:

\left(x-h\right)^2 + \left(y-k\right)^2 = r^2

The center of the circle is the point \left(h,k\right) and the radius is r.

Here, the equation is:

\left(x+1\right)^2+\left(y-1\right)^2=9

Therefore:

  • h=-1
  • k=+1
  • r=3

This is the equation of a circle whose center is \left(-1{,}1\right) and radius is 3. We can graph this circle as follows:

-

\left(x+3\right)^2+\left(y-2\right)^2=4

The standard form of a circle is:

\left(x-h\right)^2 + \left(y-k\right)^2 = r^2

The center of the circle is the point \left(h,k\right) and the radius is r.

Here, the equation is:

\left(x+3\right)^2+\left(y-2\right)^2=4

Therefore:

  • h=-3
  • k=2
  • r=2

This is the equation of a circle whose center is \left(-3{,}2\right) and radius is 2. We can graph this circle as follows:

-

\left(x+1\right)^2+\left(y-1\right)^2=\dfrac{1}{4}

The standard form of a circle is:

\left(x-h\right)^2 + \left(y-k\right)^2 = r^2

The center of the circle is the point \left(h,k\right) and the radius is r.

Here, the equation is:

\left(x+1\right)^2+\left(y-1\right)^2=\dfrac{1}{4}

Therefore:

  • h=-1
  • k=+1
  • r=\dfrac{1}{2}

This is the equation of a circle whose center is \left(-1{,}1\right) and radius is \dfrac{1}{2}. We can graph this circle as follows:

-

\left(x-2\right)^2+\left(y-2\right)^2=9

The standard form of a circle is:

\left(x-h\right)^2 + \left(y-k\right)^2 = r^2

The center of the circle is the point \left(h,k\right) and the radius is r.

Here, the equation is:

\left(x-2\right)^2+\left(y-2\right)^2=9

Therefore:

  • h=-2
  • k=-2
  • r=3

This is the equation of a circle whose center is \left(2{,}2\right) and radius is 3. We can graph this circle as follows:

-

\left(x-\dfrac{1}{2}\right)^2+\left(y-1\right)^2=1

The standard form of a circle is:

\left(x-h\right)^2 + \left(y-k\right)^2 = r^2

The center of the circle is the point \left(h,k\right) and the radius is r.

Here, the equation is:

\left(x-\dfrac{1}{2}\right)^2+\left(y-1\right)^2=1

Therefore:

  • h=\dfrac{1}{2}
  • k=1
  • r=1

This is the equation of a circle whose center is \left(\dfrac{1}{2},1\right) and radius is 1. We can graph this circle as follows:

-

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See also
  • Course : Circles
  • Exercise : Write equations of circles from graphs
  • Exercise : Convert equations from general to standard form
  • Exercise : Find the area/circumference of a circle
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