LESSON FIRST.
LINES.
Note to the Teacher.—In all the development-lessons, the pupils are to be occupied with the diagrams, and not with the printed matter.
See Note [A], Appendix.
Refer to Diagram [1], and show that
What are here drawn are intended to represent length only.
They have a little width, that they may be seen.
They are called lines.
A line is that which has length only.
POINTS
Show that
Position is denoted by a point.
It occupies no space.
It has some size, that it may be seen.
The ends of a line are points.
A line may be regarded as a succession of points.
The intersection of two lines is a point.
A point is named by placing a letter near it.
Diagram 1.
A point may be represented by a dot. The point is in the center of the dot.
A point is that which denotes position only.
A line is named by naming the points at its ends.
Read all the lines in Diagram [1].
CROOKED LINES.
See Note [B], Appendix.
Does the line m n change direction at the point 1?
At what other points does it change direction?
It is called a crooked line.
A crooked line is one that changes direction at some of its points.
CURVED LINES.
The line o p changes direction at every point.
It is called a curved line.
A curved line is one that changes direction at every point.
STRAIGHT LINES.
Does the line i j change direction at any point?
It is called a straight line.
A straight line is one that does not change direction at any point.
OTHER LINES.
The line q r winds about a line.
It is called a spiral line.
The line w x winds about a point.
It also is called a spiral line.
A spiral line is one that winds about a line or point.
The line 7 8[[1]] looks like waves.
[1]. To be read seven, eight, not seventy-eight.
It is called a wave line.
What kind of a line is a b?
Why? What is a straight line?
What kind of a line is 11 16?
Why? What is a crooked line?
What kind of a line is o p?
Why? What is a curved line?
What kind of a line is s t?
Why?
What kind of a line is 9 10?
Why? What is a spiral line?
What kind of a line is w x?
Why?
