Circles

Surface Area of a Cylinder

2(pi*r^2)+2*pi*r*h

Area of a Sector Formula

=[n/360]*Area of Circle

Central Angle

A central angle is an angle formed by two radii.

Chord

A chord is a line segment joining two points on the circle

Circle Definition

A circle is the set of all points in a plane at the same distance from a certain point. This point is called the center of the circle. A circle is labeled by its center point: circle O means the circle with center point O.

Tangent

A line that touches only one point on the circumference of the circle is tangent to that circle. A line drawn tangent to a circle is perpendicular to the radius at the point of tangency.

Radius

A radius is a line segment from the center of the circle to any point on the circle. The radius of a circle is one-half the length of the diameter.

Sector

A sector is a portion of the circle bounded by two radii and an arc

Arc

An arc is a portion of the circumference of a circle.

Arc Length of Inscribed Angle

An inscribed angle also has a relationship with minor arc length. For an inscribed angle measuring n degrees, Arc length = [n/180] × circumference In other words, an angle that's inscribed defines an arc twice as long as one defined by a central angle of equal angle measure.

Inscribed Angle

An inscribed angle is one that opens up from the edge of a circle instead of its center

Area of a Circle

Area =pi*r^2

Diameter of a Circle

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for the diameter of a sphere

Circumference Formula

Since π equals the ratio of the circumference to the diameter, a formula for the circumference is C = πd or C = 2πr

Circumference

The distance around a circle is called the circumference. The number π ("pi") is the ratio of a circle's circumference to its diameter. The value of π is 3.14159265 . . . , usually approximated as 3.14. For the GMAT, it is usually sufficient to remember that π is a little more than 3.

Arc Length

The length of an arc is the same fraction of a circle's circumference as its degree measure is of the degree measure of the circle (360°). For an arc with a central angle measuring n degrees, Arc length = [n/360] × circumference => [n/360] ×2πr

Minor Arc

The shorter distance between A and B along the circle is called the minor arc

Concentric

Two circles of different size with the same center are called concentric.

Major Arc

the longer distance is the major arc. An arc that is exactly half the circumference of the circle is called a semicircle (in other words, half a circle).