09JUL21

Slanting lines have both x and y in their equations.

A slanting line may be imagined as a ladder resting against a wall.

Suppose (a,b) is and (c,d) are the ends of the ladder.

Say (a,b) is the foot of the ladder. It's on the floor.

Say (c,d) is the top of the ladder. It's in contact with the wall.

Now (a,b) is the lower point and (c,d) is the higher point.

y=b is the equation of the floor.

It's on the vertical x=a.

x=c is the equation of the wall.

It's on the horizontal y=d.

The straight distance between (a,b) and (c,d) is the length of the ladder.


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