Chapter 4: Problem 2
Berechnen Sie die Schnittpunk te der Ebene \(2 x-5 y+3 z=1\) mit den Koordinatenachsen. Welche der folgenden Punkte licgen in der Ebene, welche unterhalb brw. oberhalb der Fbene? $$ A=(1 ; 2 ; 3), \quad B=(2 ;-3 ;-4), \quad C=(-4 ; 2 ; 0), \quad D=(0 ; 0 ; 0) $$
Short Answer
Expert verified
Intersections: (0.5, 0, 0), (0, -0.2, 0), (0, 0, 0.333). Points: A on, B above, C below, D below.
Step by step solution
01
- Calculate the intersection with the x-axis
To find the intersection with the x-axis, set y and z to 0 and solve for x in the plane equation. \[ 2x - 5(0) + 3(0) = 1 \]\[ 2x = 1 \]\[ x = \frac{1}{2} \]So, the intersection with the x-axis is \( \left( \frac{1}{2}, 0, 0 \right) \).
02
- Calculate the intersection with the y-axis
To find the intersection with the y-axis, set x and z to 0 and solve for y in the plane equation. \[ 2(0) - 5y + 3(0) = 1 \]\[ -5y = 1 \]\[ y = -\frac{1}{5} \]So, the intersection with the y-axis is \( \left( 0, -\frac{1}{5}, 0 \right) \).
03
- Calculate the intersection with the z-axis
To find the intersection with the z-axis, set x and y to 0 and solve for z in the plane equation. \[ 2(0) - 5(0) + 3z = 1 \]\[ 3z = 1 \]\[ z = \frac{1}{3} \]So, the intersection with the z-axis is \( \left( 0, 0, \frac{1}{3} \right) \).
04
- Check point A
For point A (1, 2, 3), substitute into the plane equation: \[ 2(1) - 5(2) + 3(3) = 2 - 10 + 9 = 1 \]Point A lies on the plane.
05
- Check point B
For point B (2, -3, -4), substitute into the plane equation: \[ 2(2) - 5(-3) + 3(-4) = 4 + 15 - 12 = 7 \]Point B lies above the plane.
06
- Check point C
For point C (-4, 2, 0), substitute into the plane equation: \[ 2(-4) - 5(2) + 3(0) = -8 - 10 = -18 \]Point C lies below the plane.
07
- Check point D
For point D (0, 0, 0), substitute into the plane equation: \[ 2(0) - 5(0) + 3(0) = 0 \]Point D lies below the plane.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Coordinate Axes Intersections
The intersections of a plane with the coordinate axes are essential foundational points in geometry. To find these intersections, you set the other two coordinates to zero and solve for the remaining variable in the plane's equation. Let's break it down:
● **X-axis Intersection:** When y and z are set to zero, solving the given plane equation simplifies to finding x.
● **Y-axis Intersection:** When x and z are set to zero, solving the equation simplifies to finding y.
● **Z-axis Intersection:** When x and y are set to zero, solving the equation simplifies to finding z.
Understanding this helps in visualizing how a plane cuts through three-dimensional space.
● **X-axis Intersection:** When y and z are set to zero, solving the given plane equation simplifies to finding x.
● **Y-axis Intersection:** When x and z are set to zero, solving the equation simplifies to finding y.
● **Z-axis Intersection:** When x and y are set to zero, solving the equation simplifies to finding z.
Understanding this helps in visualizing how a plane cuts through three-dimensional space.
Point Position Relative to Plane
Determining whether a point lies on, above, or below the plane involves substituting the point's coordinates into the plane equation. Here's the trick:
1. Substitute the point's coordinates into the plane's equation.
2. Solve for the value.
For example, with our plane equation \(2x - 5y + 3z = 1\) and point A(1, 2, 3):
here's the substitution: \(2(1) - 5(2) + 3(3) = 2 - 10 + 9 = 1\).
This shows point A lies on the plane.
If a point does not satisfy the plane equation precisely (i.e., it results in a number other than the plane's constant term), it's either above or below, depending on the sign of the resultant value.
1. Substitute the point's coordinates into the plane's equation.
2. Solve for the value.
For example, with our plane equation \(2x - 5y + 3z = 1\) and point A(1, 2, 3):
here's the substitution: \(2(1) - 5(2) + 3(3) = 2 - 10 + 9 = 1\).
This shows point A lies on the plane.
If a point does not satisfy the plane equation precisely (i.e., it results in a number other than the plane's constant term), it's either above or below, depending on the sign of the resultant value.
Plane Equation Solutions
Understanding plane equations is key. A plane equation usually has the format \(Ax + By + Cz = D\). Each coefficient (A, B, C) influences the plane's orientation.
To solve, you:
• Set coordinates to zero for one of the axes.
• Solve the simplified equation for the remaining variable.
For instance, finding the intersection with the x-axis in our plane equation \(2x - 5y + 3z = 1\) , we set y and z to zero:
\(2x = 1\), so \(x = \frac{1}{2}\). This intersection point, therefore, is \(\frac{1}{2}, 0, 0\).
To solve, you:
• Set coordinates to zero for one of the axes.
• Solve the simplified equation for the remaining variable.
For instance, finding the intersection with the x-axis in our plane equation \(2x - 5y + 3z = 1\) , we set y and z to zero:
\(2x = 1\), so \(x = \frac{1}{2}\). This intersection point, therefore, is \(\frac{1}{2}, 0, 0\).
Analytical Geometry Methods
Analytical geometry allows us to use algebraic methods to solve geometric problems. This field bridges algebra and geometry via coordinate systems.
Key methods include:
• **Substitution:** Plugging coordinates into equations to test point positions.
• **Solving systems:** Making use of both the plane equation and coordinate values to find intersections.
Through these methods, we step from abstract concepts to concrete solutions, making it easier to visualize and understand the geometric relationships in three-dimensional space.
Key methods include:
• **Substitution:** Plugging coordinates into equations to test point positions.
• **Solving systems:** Making use of both the plane equation and coordinate values to find intersections.
Through these methods, we step from abstract concepts to concrete solutions, making it easier to visualize and understand the geometric relationships in three-dimensional space.