Plane P contains four distinct lines l 1, l 2, l 3, and l 4. Suppose l 1 perpendicular to l 2, l2 perpendicular to l 3, and l 3 perpendicular to l 4. How are l 1 and l 4 related?

Lines 1 and 4 will be perpendicular also.

To do this problem, you have to draw out all of the lines. Lines that are perpendicular cross at right angles. Start with lines 1 and 2, then add 3, then 4. You will see that lines 1 and 4 are also perpendicular. The pattern goes around a complete rotation.