Find the point of intersection of the given plane (y = −17) and the line that is perpendicular to the given plane and passes through (4, 8, 3).

Respuesta :

Answer:

The point of intersection is [tex]\left[\begin{array}{c}4&-17&3\end{array}\right][/tex]

Step-by-step explanation:

In order to find the intersection point we will need to find the vector equation of the line.

The plane equation is [tex]y=-17[/tex]

Now to find the line that is perpendicular to this plane, we can do the following reasoning :

The plane and the line will be perpendicular between each other if and only if the direction vector of the line is a scalar multiple from the normal vector of the plane.

The plane equation is [tex]y=-17[/tex]. Then any vector with the following form :

[tex]\left[\begin{array}{c}0&a&0\end{array}\right][/tex]

With [tex]a[/tex] ∈ IR , [tex]a\neq 0[/tex] will be perpendicular to the plane.

Let's choose [tex]a=1[/tex] to simplify the calculations.

The normal vector of the plane is [tex]\left[\begin{array}{c}0&1&0\end{array}\right][/tex]

Now the direction vector of the line must be a scalar multiple of this vector ⇒ [tex]V=b\left[\begin{array}{c}0&1&0\end{array}\right][/tex]    , [tex]b[/tex] ∈ IR

Let's also choose [tex]b=1[/tex] in order to simplify the calculations.

The vectorial equation of the line is :

[tex]\left[\begin{array}{c}x&y&z\end{array}\right]=\alpha V+P[/tex]      with [tex]\alpha[/tex] ∈ IR

Where [tex]V[/tex] is the direction vector and [tex]P[/tex] is any point where the line passes through.

Using the data from the question we complete our equation with :

[tex]IL=\left[\begin{array}{c}x&y&z\end{array}\right]=\alpha\left[\begin{array}{c}0&1&0\end{array}\right]+\left[\begin{array}{c}4&8&3\end{array}\right][/tex]     with [tex]\alpha[/tex] ∈ IR

Now let's find the intersection point between the plane [tex]y=-17[/tex] and the line [tex]IL[/tex]

This intersection point must belong to the line and also to the plane.

In order to belong to the plane its second component must be [tex]-17[/tex]

Knowing this and using the vector equation of the line we obtain this equation :

[tex]\alpha +8=-17[/tex] ⇒ [tex]\alpha =-25[/tex]

Using [tex]\alpha =-25[/tex] in the vector equation of the line we find that the point is

[tex]\left[\begin{array}{c}4&-17&3\end{array}\right][/tex]

This point belongs to the plane (because its second component is [tex]-17[/tex]) and also to the line (because it can be obtained using the vector line equation with [tex]\alpha =-25[/tex]).

Q&A Education