Tangent, Normal and Binormal Vectors — Question 6

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Question 6

For r→(t)=⟨cost,sint,t⟩\vec r(t)=\left\langle\cos t,\sin t,t\right\rangle at t=0t=0, find equations of the normal, osculating, and rectifying planes. State which Frenet vectors span each plane.

Original worksheet page 1: question and worked solution for 6-8-006
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Question 6 – Solution

Strategy Use the frame from the helix and choose the Frenet vector perpendicular to each named plane.

See the diagram in the original worksheet below.

Frame and point At t=0t=0, P=(1,0,0)P=(1,0,0), 𝑻∥⟨0,1,1⟩\mathbf T\parallel\left\langle 0,1,1\right\rangle, 𝑵=⟨−1,0,0⟩\mathbf N=\left\langle-1,0,0\right\rangle, and 𝑩∥⟨0,−1,1⟩\mathbf B\parallel\left\langle 0,-1,1\right\rangle.

Planes The normal plane is perpendicular to 𝑻\mathbf T: y+z=0\boxed{y+z=0}, and is spanned by 𝑵,𝑩\mathbf N,\mathbf B. The osculating plane is perpendicular to 𝑩\mathbf B: −y+z=0\boxed{-y+z=0}, spanned by 𝑻,𝑵\mathbf T,\mathbf N. The rectifying plane is perpendicular to 𝑵\mathbf N: x=1\boxed{x=1}, spanned by 𝑻,𝑩\mathbf T,\mathbf B.

Original worksheet page 2: question and worked solution for 6-8-006

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