- #1

Dank2

- 213

- 4

## Homework Statement

Proof that if the slopes of two lines a1, a2 (that are not vertical), m1,m2 satisfy:

m1*m2 = -1, then the lines are perpendicular.

## Homework Equations

## The Attempt at a Solution

I tried to use the tan function, so that m1 = tanΘ where Θ

_{1}is the angle of the line formed from x axis.

and m2 = tanΘ

_{2}.

now tanΘ

_{2}*Θ

_{1}= -1,

I tried using the tan(Θ1+Θ2) = but after simplifing i got (tanΘ1 - tankΘ2)/2

not sure if I am on the right way, rather solve it using trig.

ok found the answer, i had to use the points (1,m1), (1, m2), form a triangle and check for Pythagorean theorem.

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