Parallel And Perpendicular Lines              

                     Lesson 1

Parallel Lines have the same slope.

The symbol of parallel is two vertical bars.

L₁ ║ L₂   where L₁and L₂ are lines and m₁ and m₂ are slopes.

Perpendicular lines have negative reciprocal slopes.

The symbol to indicate perpendicular lines is ┴ .

T₁ ┴ T₂ are lines and m_1, m₂ are slopes T₁ ┴ T₂ → m₁ = -1/m₂

Problem:    The slope of l_k is 4/5 and l_j ┴ l_k Find the slope of l_k.

Solution      Lines l_j , l_k are perpendicular. L_j ┴ l_k

Step 1:

Solution    Since the lines are perpendicular the slopes are the same.

Step 2:

Solution    The slope of l_k is −5/4

Step 3:  

                                                            Solution    Answer: Slope = −5/4

Step 4:

Complete

                                                            Try two practice problems:

A.	l1 ┴ l2  . If the slope of l1 is 2/3 and slope of l2 is 4x − 2. Find the value of x.
B.	Determine the slope of line perpendicular to a line whose slope is -13/15.

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