Inside Outside on the Circle Circle Equations

The distance halfway across the circle is called the...

• radius
• diameter
• circumference
• area

The distance from the center of the circle to any point on the circle is called the...

• radius
• diameter
• circumference
• area

The equation of a circle with the center about the origin is:

• x² + y² = r

• x² + y² = r²

• x² + r² = y²

• x² + r² = y

What does the r in the standard equation stand for?

• r is the distance of the circle

• r is the radius of the circle

• r is the x coordinate of the center of the circle

• r is the y coordinate of the center of the circle

Write the standard equation of the circle with the given center and radius; center (0,0) and radius: 3

• x²+y²=3
• x²+y²=6
• x²+y²=9

What is the equation of a circle whose diameter is 24 and whose center is at the origin?

• x²+y²=125

• x²+y²=64

• x²+y²=144

• x²+y²=576

What is the equation for this circle?

• (x+1)+(y+1)=9
• x²+y²=9
• x+y=9
• (x-1)²+(y-1)²=9

x² + y² = r² Identify r.

x² + y² = 81

• 81²

• 9²

• 9

• -9

x² + y² = r² Identify r.

x² + y² = 196

• 196²

• 14²

• 14

• -14

x² + y² = r² Identify r.

x² + y² = 169

• 13²

• 13

• 169

• -13