Find a vector normal to the plane at (2,1,7)

In summary, the problem involves finding a vector normal to a plane at (2,1,7) and a plane tangent to a paraboloid at the same point. The equations for the plane and paraboloid are given, and the solution involves using the gradient to find the normal vector for the plane tangent to the paraboloid.
  • #1
mharten1
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0

Homework Statement


This is a two part problem
A) Find a vector normal to the plane at (2,1,7)
B) Find a vector normal to the plane tangent to the paraboloid at (2,1,7)


Homework Equations



Plane: z = x + y +4
Paraboloid: z = x^2 +3y^2

The Attempt at a Solution


I'm not sure where to start. I know that a vector normal to the plane is <1,1,-1>, but that isn't at (2,1,7). Any help?
 
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  • #2
A plane has the same normal everywhere, doesn't it?
 
  • #3
Dick said:
A plane has the same normal everywhere, doesn't it?

That's what I thought at first. But it seems too easy to be the solution to both questions. I'm going to read over the section again and see if I can find anything that will be useful.
 
  • #4
mharten1 said:
That's what I thought at first. But it seems too easy to be the solution to both questions. I'm going to read over the section again and see if I can find anything that will be useful.

It's not the solution to the second question. Think about using the gradient.
 
  • #5
Dick said:
It's not the solution to the second question. Think about using the gradient.

I was able to solve it, thank you. :)
 

1. What is a vector normal to a plane?

A vector normal to a plane is a vector that is perpendicular to every vector in the plane. It is also known as the surface normal or simply the normal vector.

2. How is a vector normal to a plane calculated?

A vector normal to a plane can be calculated by finding the cross product of two non-parallel vectors in the plane. The resulting vector will be perpendicular to both of the original vectors and therefore normal to the plane.

3. Why is it important to find a vector normal to a plane?

It is important to find a vector normal to a plane because it can be used to calculate the angle between the plane and another vector, determine the direction of the plane, and solve various geometrical problems involving the plane.

4. Can a plane have more than one vector normal?

No, a plane can only have one vector normal. This is because if two vectors are perpendicular to a plane, they must also be parallel to each other, which is not possible.

5. How do you find a vector normal to a plane at a specific point?

To find a vector normal to a plane at a specific point, you can use the formula:
n = (ax + by + cz) / sqrt(a^2 + b^2 + c^2), where a, b, and c are the coefficients of the plane's equation and (x, y, z) is the point of interest. This will give you a vector that is perpendicular to the plane at the given point.

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