Circle equation review | Analytic geometry (article) | Khan Academy
Review the standard and expanded forms of circle equations, and solve problems concerning them.
Area of a circle (video) | Geometry | Khan Academy
The area of a circle is pi times the radius squared (A = π r²). Learn how to use this formula to find the area of a circle when given the diameter.
Radius, diameter, & circumference | Circles (article) | Khan Academy
Learn the relationship between the radius, diameter, and circumference of a circle.
Circumference review (article) | Geometry | Khan Academy
The easiest strategy is to plug in the values you know into the circumference formula (in your case, plug in circumference). Then, solve for r by manipulating the equation.
Writing standard equation of a circle - Khan Academy
Use the distance formula to find the length of the diameter, and then divide by 2 to get the radius. Then find the midpoint of the diameter which will be the center of the circle.
Area of a circle - Khan Academy
How can we find the area of a circle when it doesn't split neatly into unit squares? Let's rearrange a circle to make it easier to find its area.
Radius, diameter, circumference & π (video) | Khan Academy
Learn how the number Pi allows us to relate the radius, diameter, and circumference of a circle.
Circles | Geometry (all content) | Math | Khan Academy
Standard equation of a circle Learn Features of a circle from its standard equation Graphing a circle from its standard equation
Graph a circle from its standard equation - Khan Academy
Given the standard form equation of a circle, graph the circle. For example, graph the circle whose equation is (x+5)²+ (y+2)²=4.
Partial circle area and arc length - Khan Academy
The main concept is to multiply the circumference of a full circle (of the same radius) by the fraction of a circle that is associated with the arc. The circumference of a full circle of radius r …