Finding The Distance From A Paraboloid To A Plane.

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Homework Help Overview

The problem involves finding the distance from a paraboloid defined by the equation z = x² + 2y² to a plane given by 2x + 8y + z = -8. The discussion centers around the geometric relationship between the paraboloid and the plane, particularly focusing on the conditions under which their tangent plane and normal vectors are parallel.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the need to find the point on the paraboloid where the tangent plane is parallel to the given plane. There are mentions of using partial derivatives to find the normal vector of the paraboloid and comparing it to the normal vector of the plane. Questions arise about how to set up equations based on the relationship between these vectors.

Discussion Status

The discussion is ongoing, with participants exploring the relationships between the normal vectors and attempting to solve for constants that relate them. Some guidance has been offered regarding the setup of equations, but there is no explicit consensus on the next steps or solutions.

Contextual Notes

Participants are working under the constraints of the problem as posed, with a focus on understanding the geometric implications of the normal vectors and their relationships. There is an indication of confusion regarding the resolution of one of the equations involving the constant K.

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Homework Statement



Find the distance from the paraboloid z = X2 + 2Y2 to the plane
2X + 8Y + Z = -8.


Homework Equations



The partial derivatives with respect to X, And Y for the paraboloid.



The Attempt at a Solution



My professor said we need to find the point where the tangent plane of the paraboloid is parallel to the plane. I can take the X, and Y partial derivatives, but then I do not know what to do.
 
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You should know what the normal vector to the plane is by looking at it. You want to find a point on the paraboloid whose normal vector is parallel to that. How would you find a normal vector to the surface at a point (x,y,z)?
 
Oh I just need to move the Z over then take the gradient.
 
Baumer8993 said:
Oh I just need to move the Z over then take the gradient.

Yes, and the simple way to check if two vectors are parallel is to see if one is a multiple of the other.
 
Ok, so now I am stuck at the finding the vectors that are parallel. I know that they can be a multiple of each other. I got the gradient of < 2X, 4y, -1>. I know the normal vector is
<2, 8, 1>.

I set the equations to make:

2X = 2K 4Y = 8K -1 = 1K

K is just a constant. How do I solve these?
 
Baumer8993 said:
Ok, so now I am stuck at the finding the vectors that are parallel. I know that they can be a multiple of each other. I got the gradient of < 2X, 4y, -1>. I know the normal vector is
<2, 8, 1>.

I set the equations to make:

2X = 2K 4Y = 8K -1 = 1K

K is just a constant. How do I solve these?

Good job setting the equations up, but I'm having a hard time figuring out why you can't solve -1=1*K. Take another look at them.
 
Last edited:

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