Perpendicular lines intersect one another at 90-degree angles. The slope of a line charts its vertical climb or descent over a specified horizontal distance. The slopes of perpendicular lines can be identified through their combined product. When two slopes are perpendicular, multiplying them together will equal -1. To find a perpendicular slope, you must begin with the slope of the original line and calculate what number that when combined with it would equal the desired product.
Instructions
-
-
1
Obtain a line's slope. For this example, let the slope be 5/6.
-
2
Calculate the reciprocal of the slope by inverting the numerator and denominator. In this example, the reciprocal of 5/6 is 6/5.
-
-
3
Multiply the reciprocal by -1 to obtain the perpendicular slope. Concluding this example, 6/5 multiplied by -1 equals -6/5. The perpendicular slope is -6/5.