- #1

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## Homework Statement

Suppose [tex]\alpha[/tex] is a regular curve in [tex]\mathbb{R}^3[/tex] with arc-length parametrization such that the torsion [tex]\tau(s)\neq 0[/tex], and suppose that there is a vector [tex]Y\in \mathbb{R}^3[/tex] such that [tex]<\alpha',Y>=A[/tex] for some constant A. Show that [tex]\frac{k(s)}{\tau(s)}=B[/tex] for some constant B, where k(s) is the curvature of alpha.

## The Attempt at a Solution

I think the Frenet formula in question that I can use is [tex]n'=-kt-\tau b[/tex], but I can't make it work.