FORMS - Circle

Circles are considered congruent if they have the same radius. The diameter of a circle is its longest chord. Chords of equal length in a circle subtend equal angles at the center, and a radius drawn perpendicular to a chord bisects that chord. Circles with different radii are similar. A circle can circumscribe shapes such as a rectangle, trapezium, triangle, square, or kite, and it can also be inscribed within a square, triangle, or kite. Chords that are equidistant from the center of a circle are equal in length, and the distance from the center to the diameter, the longest chord, is zero. As the length of a chord increases, the perpendicular distance from the center decreases. Tangents drawn at the ends of the diameter are parallel to each other. An isosceles triangle is formed when the radii connect the ends of a chord to the center of the circle.