- #1

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## Homework Statement

The line l has equation y = 3x + 4

Cans someone xplain how [tex]y = -\frac{1}{3}x-4[/tex] is perpendicular to line l(bisects l at 90°)

## Homework Equations

y = mx + c

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- Thread starter thomas49th
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- #1

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The line l has equation y = 3x + 4

Cans someone xplain how [tex]y = -\frac{1}{3}x-4[/tex] is perpendicular to line l(bisects l at 90°)

y = mx + c

Last edited:

- #2

cristo

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What condition must the gradients of two perpendicular lines satisfy?

- #3

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negtive gradient.

y = mx + c where m is a negitive number?

y = mx + c where m is a negitive number?

- #4

HallsofIvy

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Those can both be derived from properties of the tangent function.

- #5

cristo

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andparallel if and only if (m._{1})(m_{2})= -1

Just correcting a typo: you mean

- #6

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cant it beperpendicular if and only if (m1)(m2)= -1.

perpendicular if and only if (m1)(m2)= -0.5? Or any other number there? Was that just an example? If not what is so special about -1?

(m1)(m2)= -1

so 3 * -1/3 = -1

cheerz, Big help

- #7

Integral

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Now using the graphs, compute the slopes, can you now see why the relationship is [itex] m_1 m_2 = -1 [/itex]

You may need to look at several sets of lines to see the relationships.

- #8

HallsofIvy

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Thomas49th, are you saying you cannot read our responses?

- #9

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aha, ingenius. It works. Thanks a load

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