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regular smooth curve - Penn Math

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Let �: I � R 3 be parametrized by arc length, and<br />

let T(s) be the unit tangent vector along � .<br />

If the curvature �(s) � 0 , then we also have the<br />

principal normal vector N(s) at �(s) .<br />

In that case, define the binormal vector B(s) to � at s<br />

by the vector cross product,<br />

B(s) = T(s) � N(s) .<br />

Problem 10. Show that B'(s) is parallel to N(s) .<br />

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