Find the curvature at the point (x, y) on the ellipse?

[Math10]

Homework Statement

Find the curvature at the point (x, y) on the ellipse x^2/9+y^2/4=1.

Homework Equations

None.

The Attempt at a Solution

x^2/a^2+y^2/b^2=1
so I know that a=3 and b=2 for this problem.
x(t)=acos(t) and y(t)=bsin(t)
so x(t)=3cos(t) and y(t)=2sin(t)
now what? What's the formula for finding the curvature for this problem? The answer is 162/(81-5x^2)^(3/2).

 

[Delta2]

maybe this will help for what you looking for http://en.wikipedia.org/wiki/Curvature#Local_expressions

 

[micromass]

How did you define curvature?

 

[Mark44]

Homework Statement

Find the curvature at the point (x, y) on the ellipse x^2/9+y^2/4=1.

Homework Equations

None.

The Attempt at a Solution

x^2/a^2+y^2/b^2=1
so I know that a=3 and b=2 for this problem.
x(t)=acos(t) and y(t)=bsin(t)
so x(t)=3cos(t) and y(t)=2sin(t)
now what? What's the formula for finding the curvature for this problem? The answer is 162/(81-5x^2)^(3/2).

If you textbook has a problem about finding curvature, I can pretty much guaranteed that it will have a formula for curvature somewhere close by in the book. That should be the first place you look.

Also, you don't need to convert to parametric form to find the curvature.