circle

• A chord is any line segment that connects two points on the circumference of a circle.
• An arc is part of the circumference of a circle, measured from one point to another point along the circumference.
• If a diameter divides a circle into two congruent arcs, then the angles formed by these arcs are also congruent.
• Two circles are congruent if they have equal radii or diameters.
• The measure of an angle subtended at the center of a circle is twice the measure of its central angle.
• The measure of a central angle is equal to twice the measure of its intercepted arc.
• The central angle is an angle whose vertex is at the center of the circle and whose sides are radii or tangents to the circle.
• The diameter of a circle is the distance across its center, passing through both ends of the radius.
• The perimeter of a circle is the total length around the outside edge of the circle.
• The area of a circle is the amount of space inside it.
• To find the area of a sector, multiply the radius squared by the central angle in degrees divided by 360.
• The radius of a circle is half its diameter.
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