Question

How do you determine if a line is parallel or perpendicular?

Answer 1

Parallel lines: Two lines are parallel if and only if their slopes are equal. The line in the form $Ax+By=C$ has a slope of $–A/B.$

or

If two straight lines lie in the same plane, and if they never intersect each other, they are called parallel lines. They are always the same distance apart and are equidistant lines. The symbol || is used to represent parallel lines.

For example, $AB\left|\right|CD$means a line $AB$is parallel to a line $CD.$

Perpendicular lines: Two lines are perpendicular if their slopes are negative reciprocals of each other.

or

When two lines intersect each other at an angle of $90°,$ they are known as perpendicular lines. Perpendicular lines are denoted by the symbol $\perp$.

For example, $PQ\perp RS$means a line $PQ$is perpendicular to a line $RS.$