Four Ways to Determine a Plane
- A line and a point not on the line determine a plane. Hold a pencil in your left hand so that it's pointing away from you, and hold your right forefinger (pointing upward) off to the side of the pencil.
- Two intersecting lines determine a plane.
- Two parallel lines determine a plane.
On the flat coordinate plane, there are two axes, the vertical y-axis and the horizontal x-axis. The origin is the point where they intersect. This point has the coordinates 0,0 and is usually labelled with the letter O.
In geometry, a line can be defined as a straight one- dimensional figure that has no thickness and extends endlessly in both directions. It is often described as the shortest distance between any two points.
There is a unique plane which passes through P0 and has n as a normal vector. Now P lies in the plane through P0 perpendicular to n if and only if. and n are perpendicular. As = r - r0, this condition is equivalent to. This is a vector equation of the plane.
Here's the summary of our methods:
- Get the two equations for the lines into slope-intercept form.
- Set the two equations for y equal to each other.
- Solve for x.
- Use this x-coordinate and plug it into either of the original equations for the lines and solve for y.
The coordinate planes are: the xy-plane, the set of all points whose z-coordinate is zero; the yz-plane, the set of all points whose x-coordinate is zero; and the xz-plane, the set of all points whose y-coordinate is zero. The projection of a point P = (x, y, z) onto the xy-plane is the point (x, y,0).
Each pair of axes defines a coordinate hyperplane. The coordinates are often denoted by the letters X, Y, and Z, or x, y, and z. The axes may then be referred to as the X-axis, Y-axis, and Z-axis, respectively. Then the coordinate hyperplanes can be referred to as the XY-plane, YZ-plane, and XZ-plane.
For the axis intercepts, we set two variables to 0, and solve for the third variable. For example, to find the z-axis intercepts, set x = 0 and y = 0. This can be done in the original equation: 2 + 2 2 + 4 2 + 2 − 8 + 24 = −5 (0)2 + 2(0)2 + 4 2 + 2(0) − 8(0) + 24 = −5 4 2 + 24 + 5 = 0.
As with equations of lines in three dimensions, it should be noted that there is not a unique equation for a given plane. The graph of the plane -2x-3y+z=2 is shown with its normal vector.
To find a parametrization, we need to find two vectors parallel to the plane and a point on the plane. Finding a point on the plane is easy. We can choose any value for x and y and calculate z from the equation for the plane. Let x=0 and y=0, then equation (1) means that z=18−x+2y3=18−0+2(0)3=6.
Unit Normal VectorAny nonzero vector can be divided by its length to form a unit vector. Thus for a plane (or a line), a normal vector can be divided by its length to get a unit normal vector. Example: For the equation, x + 2y + 2z = 9, the vector A = (1, 2, 2) is a normal vector. |A| = square root of (1+4+4) = 3.