# Homework Help: Intersection of surfaces/tangent vector

1. Oct 13, 2004

### Odyssey

Hi, how do I find a tangent vector to the curve intersection of the surfaces $2x^2+2y^2-z^2=25$ and $x^2+y^2=z^2$ which has positive x-direction?

2. Oct 14, 2004

### arildno

Note that your last equation implies that we may write:
$$x=z\cos\theta,y=z\sin\theta,0\leq\theta\leq2\pi$$
Inserting these relations into your first equation, yields:
$$z^{2}=\frac{25}{3}$$
Can you take it from here?