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Let c(t)=x(t)i+y(t)j+z(t)k. Show that ||c(t)||=k where k is a constant if and only if c(t) and c'(t) are orthogonal.

(Note: c, i, j, and k above are vectors).

[Hint: use ||c(t)||^2 = c(t) * c(t)]

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Let c(t)=x(t)i+y(t)j+z(t)k. Show that ||c(t)||=k where k is a constant if

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