Angles are measured by degrees.
A Degree is one of the three hundred and sixty equal parts of the space about a point in a plane.
Angles are distinguished in respect to magnitude by the terms Right, Acute and Obtuse Angles.
A Right Angle is that formed by one line meeting another, so as to make equal angles with that other.
The lines forming a right angle are perpendicular to each other.
An Acute Angle is less than a right angle. See [Fig. 35].
An Obtuse Angle is greater than a right angle. See [Fig. 36].
Obtuse and acute angles are also called oblique angles; and lines which are neither parallel nor perpendicular to each other are called oblique lines.
The Vertex or Apex of an angle is the point in which the including lines meet.
An angle is commonly designated by a letter at its vertex; but when two or more angles have their vertices at the same point, they cannot be thus distinguished.