Question

1. what defines perpendicular lines?

a. lines that divide a plane into three equal parts
b. lines that share a common endpoint
c. lines that run parallel to each other
d. lines that intersect at a 90° angle

Explanation:

Perpendicular lines are defined by their intersection at a right angle ($90^{\circ}$). Option a is incorrect as it doesn't relate to perpendicularity. Option b describes lines with a common endpoint (not necessarily perpendicular). Option c describes parallel lines (which never intersect). Only option d correctly matches the definition of perpendicular lines.

Answer:

d. Lines that intersect at a \(90^{\circ}\) angle