Informal Statement 1
The sum of the angles of a triangle is equal to a striaght angle
Informal Statement 2
Two straight lines can intersect at only one point
Informal Statement 3
A line can be divided into two equal parts by only one point
Informal Statement 4
An angle can be divided into two parts by only one line
Informal Statement 5
All straight lines are equal
Informal Statement 6
All right angles are equal
Informal Statement 7
Only one perpendicular line can be drawn to a line at a point in the line
Informal Statement 8
Compliments of equal angles or of the same angle are equal
Informal Statement 9
Supplements of equal angles or of the same angle are equal
Informal Statement 10
The sum of all angles about a point on one side of a straight line through the point is a straight angle
Informal Statement 11
The sum of all angles about a point is equal to 360 degrees
Informal Statement 12
If the sum of two adjacent angles is equal to a straight angle, their exterior sides form one straight line
Informal Statement 13
When two straight lines intersect, the vertical angles formed are equal
Informal Statement 14
The sum of two sides of a triangle is greater than the third side
Informal Statement 15
In any polygon, the sum of an exterior angle and the adjacent interior angle is equal to a right angle
Informal Statemtent 16
In any polygon with n vertices, the sum of (one group of exterior angles?) and all interior angles = n straight angles