# Find the points where orthogonal

• Oct 17th 2012, 07:41 PM
Find the points where orthogonal
Consider the helix r(t) = <cost, sint, t> for [-inf, inf]. Find all points on the helix at which r and r' are orthogonal
• Oct 17th 2012, 07:53 PM
TheEmptySet
Re: Find the points where orthogonal
Quote:

Consider the helix r(t) = <cost, sint, t> for [-inf, inf]. Find all points on the helix at which r and r' are orthogonal

Well if we take the derivative we get

$\displaystyle r'(t)=<-\sin(t), \cos(t), 1>$

Two vectors are orthongal is their dot product is equal to zero, so....

Can you finish from here?

By the way how is Corvallis? I miss it alot. I would kill for Tarn Tip Thai about now.
• Oct 17th 2012, 07:53 PM
chiro
Re: Find the points where orthogonal

Can you compute r'(t)? When are two vectors orthogonal? (Hint: it has something to do with something being 0)
• Oct 17th 2012, 08:04 PM
Re: Find the points where orthogonal
Yeah, I got it from there, thanks so much!
And Corvallis is great, I'm loving it so far! (I'm a freshman, lol)
I haven't heard of Tarn Tip Thai, but it sounds good, I'll have to try it! :)
• Oct 17th 2012, 08:11 PM
TheEmptySet
Re: Find the points where orthogonal
Quote: