Unformatted text preview: Curves and curvature 1Find the arc length parameterization of a curve r(t) if the length of r’(t) is equal to a constant S>0. (Answer R(s)= r(s/S) ) Use the previous to find the curvature of a circle of radius A. Find the curvature of the helix r(t)= (A cos t, A sin t, Bt) , A>0 , B>0 (or B<0) 2Suppose r(s) is an arclength parameter curve so that r’(s) has length 1 for all s. (a) Show that r’’(s) is perpendicular to r’(s). (b) Suppose r’’(s) is not 0 and then set N= r’’(s)/  r’’(s) and κ= r”(s). Then show that dN/ds = κ T + τ (TxN) for some (numerical) τ (c) Then show that with B= TxN, dB/ds = τN (cf book problems 59,60, 61 in section 13.3) 3 Find the torsion τ for the curve r(t) = (A cos t, A sin t, Bt ) where A>0 but B can be positive , negative, or 0....
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 Winter '10
 MOSHCHOVAKIS
 Geometry, triangle, answer cos angle, arc length parameterization

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