If two non-vertical lines that are in the same plane has the same slope, then they are said to be parallel. Two parallel lines won"t ever intersect.

You are watching: Perpendicular lines intersect to form right angles

If two non-vertical lines in the same plane intersect at a right angle then they are said to be perpendicular. Horizontal and vertical lines are perpendicular to each other i.e. the axes of the coordinate plane.

**Example**

Compare the slope of the perpendicular lines

The slope of the red line:

$$m_1=frac-3-22-left ( -3 ight )=frac-55=-1$$

The slope of the blue line

$$m_2=frac2-left ( -2 ight )3-left ( -1 ight )=frac44=1$$

The slopes of two perpendicular lines are negative reciprocals.

See more: How Many Pints Are In 32 Ounces To Pints, Convert 32 Ounces To Pints

The product of the slopes of two perpendicular lines is -1 since

$$mcdot -frac1m=-1,: : where: : m_1=m: : and: : m_2=-frac1m$$

**Video lesson**

Are these two line parallel?

**More classes on this subject**

Algebra 1Formulating linear equations: Writing linear equations using the slope-intercept formAlgebra 1Formulating linear equations: Writing linear equations using the point-slope form and the standard form

## Next Chapter:

FORMULATING LINEAR EQUATIONS – Scatter plots and linear models

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