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Q. 60

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Calculus
Found in: Page 873
Calculus

Calculus

Book edition 1st
Author(s) Peter Kohn, Laura Taalman
Pages 1155 pages
ISBN 9781429241861

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Short Answer

Prove that the tangent vector is always orthogonal to the position vector for the vector-valued function.

r(t)=sint,sintcost,cos2t

Ans:

r(t)·r'(t)=(isint+jsintcost+kcos2t)·(icost+jcos2t-ksin2t)r(t)·r'(t)=0

See the step by step solution

Step by Step Solution

Step 1. Given information: 

r(t)=sint,sintcost,cos2t

Step 2. Proving that the tangent vector is always orthogonal to the position vector for the vector-valued function:

r(t)=sint,sintcost,cos2tr(t)=isint+jsintcost+kcos2t

Differentiate with respect to t

r'(t)=icost+jcos2t-ksin2t

Find r(t)·r'(t)

r(t)·r'(t)=isint+jsintcost+kcos2t·(icost+jcos2t-ksin2t)r(t)·r'(t)=0

Thus, the tangent vector is always orthogonal to the position vector for the vector-valued function.

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