Find the equation of the plane given a point and two planes

In summary, to find the equation of the plane passing through (1,3,8) and perpendicular to the line of intersection of the planes 3x−2z+1=0 and 4x+3y+7=0, you need to take the cross product of the two normals to get the direction vector, and then use this vector and the given point in one of the forms of the equation of a plane.
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sawdee
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I've done a question similar to this, however this one has no complete equations i can solve for.

Determine the equation of the plane that passes through (1,3,8) and is perpendicular to the line of intersection of the planes 3x−2z+1=0 and 4x+3y+7=0.

I know to take the cross product of the two normals to get my new direction vector, but I am stuck at that point. What form should this be written in and further, can I use the given point?
 
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  • #2
sawdee said:
I've done a question similar to this, however this one has no complete equations i can solve for.
You're asked to find the equation of the plane with the given point

sawdee said:
Determine the equation of the plane that passes through (1,3,8) and is perpendicular to the line of intersection of the planes 3x−2z+1=0 and 4x+3y+7=0.

sawdee said:
I know to take the cross product of the two normals to get my new direction vector,
Yes, that will work.

sawdee said:
but I am stuck at that point. What form should this be written in and further, can I use the given point?
There are several different forms of the equation of a plane, so unless the grader is especially particular, it doesn't matter much what form you use.
You have to use the given point in order to get a unique plane. If N is the direction of the intersection of the given planes (and hence is normal to the plane you want), then the equation of the plane is ##n_1(x - 1) + n_2(y - 3) + n_3(z -8) = 0##, where ##\vec N = <n_1, n_2, n_3>##.
 
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FAQ: Find the equation of the plane given a point and two planes

What is the equation of a plane?

The equation of a plane in 3-dimensional space is represented as Ax + By + Cz + D = 0, where A, B, and C are the coefficients of the x, y, and z variables and D is a constant.

How do I find the equation of a plane given a point and two planes?

To find the equation of a plane given a point and two intersecting planes, you can use the cross product of the normal vectors of the two given planes. The resulting vector will be perpendicular to both planes and can be used as the coefficients A, B, and C in the equation of a plane. Then, plug in the coordinates of the given point to solve for the constant D.

Can I use the equation of a plane to find the distance between a point and the plane?

Yes, the equation of a plane can be used to find the shortest distance between a point and the plane. This distance is represented as the absolute value of (Ax + By + Cz + D) divided by the square root of (A^2 + B^2 + C^2).

What is the significance of the normal vector in the equation of a plane?

The normal vector in the equation of a plane represents the perpendicular direction to the plane. It is important because it can be used to determine the orientation and slope of the plane, as well as its distance from the origin.

Are there any other methods for finding the equation of a plane given a point and two planes?

Yes, there are other methods such as using the point-normal form of a plane, where the equation is represented as (r - r0) • n = 0, with r representing a general point on the plane, r0 representing the given point, and n representing the normal vector. You can also use the point-slope form of a plane, where the equation is represented as z = z0 + a(x - x0) + b(y - y0), with (x0, y0, z0) representing the given point and a and b representing the slopes of the plane in the x and y directions, respectively.

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