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# Introduction to Angles of Elevation and Depression

Any surface which is parallel to the surface of the earth is said to be horizontal. For example, the surface of liquid in a container is always horizontal, even if the container is held at an angle.

The floor of your classroom is horizontal. Any line drawn on horizontal surface is will also be horizontal. Any line or surface which is perpendicular to a surface is said to be vertical. The walls of your classroom are vertical. A plum-line is a mass which hangs freely on a thread.

1. Say whether the following are horizontal or vertical, or neither:

a. the table top

b. the door

c. the pictures

d. the floor boards

e. the back of the chair

f. the table legs

g. the ruler (on the table)

h. the line where the walls meet

i. the brush handle

j. the top edge of the small

# Elevation and Depression

Suppose that you are looking at an object in the distance.

If the object is above you, then the angle of elevation is the angle your eyes look up.

If the object is below you, the angle of depression is the angle your eyes look down.

Angles of elevation and depression are measured from the horizontal.

It is common mistake not to measure the angle of depression from the horizontal…