1. The problem statement, all variables and given/known data If c is given in terms of some other parameter t and c'(t) is never zero, show that k = ||c'(t) x c"(t)||/||c'(t)||3 The first two parts of this problem involved a path parametrized by arc length, but this part says nothing about that, so I assume that this path is not parametrized by arc length. 2. Relevant equations I have found that T'(t) = c"(t) = [||c'(t)||2c"(t) - c'(t)(c'(t) dot c"(t))]/||c'(t)||3 I am having trouble figuring out how to relate the curvature to the equation k = ||c'(t) x c"(t)||/||c'(t)||3 3. The attempt at a solution I can express the equation as the components so F(x,y,z) = [(z"y'-y"z')2+(x"z'-x'z")2(y"x'-x'y")2]1/2/(x'2+y'2+z'2)3/2 Where should I go from here, and is the above equation useful at all? Do I need to find ||c"(t)|| as well (and is that even possible)?