Although I have full information about the arc, I still don't know how to draw it. Precisely, I don't understand the explanation of the directions that I have.
Here is the information that I have:
Start point X=-40.0 Y=0.0 Z=0.0
End point X=40.0 Y=0.0 Z=0.0
Center X=0.0 Y=0.0 Z=0.0
Radius = 40.0
Direction X=-0.0 Y=-0.0 Z=-1.0
Direction X=-1.0 Y=0.0 Z=0.0
I put two possibilities. Please, can anyone tell which of them is the right one? and why? based on the information that I've mentioned.enter image description here
The direction should be a tangent vector to specify what plane the arc is in. I take the first direction to say the half circle is in the $xz$ plane and below the $x$ axis. The second says the circle is in the $xy$ plane on the $+y$ side of the $x$ axis.