life easier to be able to recognize them. The first is the 30º-60º-90º triangle,
whose sides are always in the ratio 1 : : 2.
In the 45º-45º-90º triangle, the ratio is 1 : 1 : Circles: A circle is a . . . well, you know what a circle is. What you need to
remember about the circle for the SAT is that the radius is the distance from the
center of a circle to any point on its circumference (or perimeter of the circle).
The diameter is twice the radius and connects a point on the edge to its opposite
point through the center. This is not to be confused with a chord, which just
connects any two points on the circumference.
Here are some formulas for the components of a circle:
area = π × r^2 (r is radius)
circumference = 2 × π × r
arc = measure of central angle
arc also = 2 × measure of inscribed angle