Angle Pairs
Complementary and Supplementary Angles
Special names are given to pairs of angles whose sums equal either 90 or 180 degrees. A pair of
angles whose sum is 90 degrees are called complementa
Dimension
Dimension is a characteristic of all geometric regions, objects, and spaces. The previous sections
have probably already made you aware of the concept of dimension. It is roughly the number
Parallel Lines
Because lines extend infinitely in both directions, every pair of lines either intersects once, or don't
intersect at all. The pairs of lines that never intersect are called parallel li
Dividing Angles and Segments
Dividing Angles
Angles can be divided just like ordinary numbers. An angle can only be divided by a ray on the
interior of the angle, though. Such a ray that divides an an
Lines
Lines
A line is the infinite set of all points arrayed in a straight formation. It is difficult to formally define, but
easy to understand. A line has no thickness; it has only length, and can b
Angles
An angle is a geometric figure consisting of two rays with a common endpoint. It looks like this:
Figure %: Angle ABC
The common endpoint is called the vertex of the angle; in this case the ver
Planes
A plane is a boundless surface in space. It has length, like a line; it also has width, but not thickness.
A plane is denoted by writing "plane P", or just writing "P". On paper, a plane looks
Perpendicular Lines
Lines (or segments) are called perpendicular if their intersection with one another forms a right
angle. You can see for yourself that if one of the angles formed by the intersecti
Space
So far we have dealt with points, lines, and planes. All of these lie within space. Space is the
collection of all points. It has no shape, and it has no limits. Space is three-dimensional; that
Terms
Acute Angle - An angle whose measure is less than 90 degrees.
Adjacent Angle - Angles that share a vertex, one side, and no interior points.
Alternate Exterior Angles - Angles created when a tra