# Thread: curvature and parametric equations

1. ## curvature and parametric equations

When i take the cross product of r' and r'' im getting 0, so thats my problem on this one....
Find the curvature of the curve

and on this one im having trouble figuring out where to start

Find parametric equations for the tangent line at the point
on the curve
=
=
=

Thanks in advance, i really just need help getting started on these.

2. Originally Posted by casesam
When i take the cross product of r' and r'' im getting 0, so thats my problem on this one....
Find the curvature of the curve

and on this one im having trouble figuring out where to start

Find parametric equations for the tangent line at the point
on the curve
=
=
=

Thanks in advance, i really just need help getting started on these.
Hi

As far as I remember the curvature is the norm of vector r"(t)
You just have to calculate the coordinates of r"(t) and then its norm

One vector of the tangent line is r'(t=-2pi/6)
As soon as you get its coordinates (a,b,c) you can have the parametric equation of the tangent line
x(t) = at + cos(-2pi/6)
y(t) = bt + sin(-2pi/6)
z(t) = ct + (-2pi/6)