As you can see, the inscribed angle is an angle made by drawing two lines
from a point on a circle’s circumference. The degree of the arc is always 2 times
that of the angle, so if the angle is 35º, the arc is 70º.
I actually didn’t know this. You truly learn something new every day.
—Samantha
Radians: Angles are usually measured in degrees (with 360 degrees in a full
circle). However, the SAT will sometimes ask you to calculate angles in terms of
radians. A radian is an arc or angle measure equal to one radius length.
Because the circumference of a circle is always proportional to its radius, there
are always 2π radians in every circle. So 360 degrees = 2π radians. To convert
from degrees to radians just multiply by π/180. To convert from radians to
degrees, just multiply by ^180 /π. For example, a 30 degree angle is the same as
(π/180) × 30 = π/6 radians.
Area: Area is the region inside a two-dimensional shape.
Circle: area = π × r 2
Rectangle: area = length (l) × width (w)
Triangle: area = (½) × base (b) × height (h). The (½) comes in because the
triangle is ½ as large as a rectangle with the same base and height.
Parallelogram: area = b × h, but the height is not one of the sides (unless the
parallelogram is also a rectangle).