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.