Angle relationships between perpendicular lines are also important. Knowing that the wall of your home is perpendicular to the floor, or that a fence post is perpendicular to a level line along the ground is really important to ensure that your home or a fence has structural integrity.

To investigate perpendicular lines, open the following exercise and follow the instructions below:

Parallel and Perpendicular Lines

1. Click on a red or blue point and move the line around.
2. Observe the angles.
3. Return to Epslien when you have completed your investigation.

Respond to the questions below in your notes.

What did you notice as you dragged point A, B, or P around the sketch? Record your observations on the topics below. Click the links below to check your answers.

1. How many right angles are created by perpendicular lines?
   Interactive popup. Assistance may be required. Check Your Answer There are 4 right angles created by 2 perpendicular lines.
2. Does the orientation of the perpendicular lines affect the angle measured? Why or why not?
   Interactive popup. Assistance may be required. Check Your Answer Notice that the orientation does not affect the angle relationship. The definition of perpendicular lines is two lines that meet at a right angle, and right angles are not necessarily oriented vertically or horizontally.

Summarize what you have learned about the angle relationships between parallel and perpendicular lines.