Lesson Eleventh Relations of Lines
Perpendicular Lines
What kind of angles do the lines a b and c d make with each other? (Diagram 11.)
Then they are perpendicular to each other.
What line is perpendicular to x y?
Why is it perpendicular to it?
What line is perpendicular to z 1?
When is a line said to be perpendicular to another?
Can a line standing alone be properly called a perpendicular line?
What two lines are perpendicular to the lines r s?
Is the line g h perpendicular to the line i j? Why?
What other line is perpendicular to the line i j?
Read three lines that are perpendicular to the line a b.
Parallel Lines
Do the lines k l, m n, differ in direction? Then do they form any angle with each other?
They are said to be parallel to each other.
Read four other lines that are parallel with k l.
What line is parallel with 2 10?
Why?
Lines are parallel with each other when they do not differ in direction.
Oblique Lines
What kind of angles do the lines u t and 8 9 form with each other?
Then they are said to be oblique to each other.
Lines are oblique to each other when they form oblique angles.
See Note C, Appendix.