Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

I am confused now,

I have a 2D line. If its equation is $r = x\cos(\theta) + y\sin(\theta)$, then what will be the line which is perpendicular to that line?

Where $r, \theta$ is described here.

I know this is very simple, any suggestions please. thanks

share|improve this question

1 Answer 1

up vote 1 down vote accepted

A line perpendicular to your line is

$$-x \sin{\theta} + y \cos{\theta} = C$$

That said, looking at your reference, that equation is the equation of a line perpendicular to a radius vector from the origin at angle $\theta$ with respect to the positive $x$ axis, at a distance $r$ from the origin.

share|improve this answer
    
thank you very much. what is the general rule to get it, please. wish to learn –  niro Feb 17 '13 at 11:31
    
Then general rule is a line perpendicular to $a x + b y = c_1$ is $-b x + a y = c_2$. –  Ron Gordon Feb 17 '13 at 11:34
    
sorry for making confuse. i would like to know how it decide.. does make a vector? if so it wil be rotated vector, then how it would be... –  niro Feb 17 '13 at 11:35

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.