can someone explain why when z=0 , n =k https://www.flickr.com/photos/123101...3/14096908607/
can someone explain why when z=0 , n =k https://www.flickr.com/photos/123101...3/14096908607/
How much do you know about vector geometry?
Do you know that $\vec{i}=<1,0,0>,~\vec{j}=<0,1,0>,~\&~\vec{k}=<0,0 ,1>,$ is the basics for vector spaces.
$\vec{i}$ is the normal for the $yz$-plane; $\vec{j}$ is the normal for the $xz$-plane; $\vec{k}$ is the normal for the $xy$-plane.
It seems to me that you are very confused about all of this material.
Is this an online course?
If you are still confused, perhaps this will help. The coefficients for $\displaystyle x$ and $\displaystyle y$ are both zero. So, the plane $\displaystyle z=0$ is the same as
$\displaystyle 0\cdot x + 0\cdot y + 1\cdot z = 0$
So, the normal is:
$\displaystyle \vec{n} = 0\cdot \vec{i} + 0\cdot \vec{j} + 1 \cdot \vec{k}$
You find the normal for that plane just as you would find the normal for any other plane.