Finding parametric equations of a tangent line

[grog]

Homework Statement

Find parametric equations of the tangent line at the point (-2,2,4) to the curve of intersection of the surface z=2x²-y² and the plane z=4

Homework Equations

Not sure

The Attempt at a Solution

Not sure quite how to approach this. take the gradient of 2x^2-y^2 and just plug for x=rcos$$\Theta$$ and y=r sin$$\Theta$$ ?

That seems too simple..

 

[Dick]

The gradient gives you a normal direction for each surface. Then the tangent is perpendicular to both normals. How can you find a vector perpendicular to two other vectors?

 

[grog]

so I would end up with 4x-2y and zero for the two normal vectors? and then take the cross product of the two? I think I may be confusing some concepts here.

 

[Dick]

so I would end up with 4x-2y and zero for the two normal vectors? and then take the cross product of the two? I think I may be confusing some concepts here.

Probably. The gradient is a vector. Those don't look like vectors. Better check the definition of 'gradient'.