' - - File: V_Vec2.txt

' Find the directional derivative of F{x,y,z} = x * y  + y*z + x*z + x*y*z in the direction of
'      v = <-2,1,3> at the point (1,1,1).

F{x,y,z} =x*y + y*z + x*z + x*y*z
Fx{x} = Diff[F,x]                           ' Partial with respect to x.
Fy{y} = Diff[F,y]                           ' Partial with respect to y.
Fz{z} = Diff[F,z]                          ' Partial with respect to z.

V<t> = <-2, 1, 3>
U<t> = vUnit[V]                           ' Unit vector.- - V / |V|
Fp<t> = <Fx, Fy, Fz>

Dr{t} = sDot[U,Fp] 

<x = 1 ; y = 1; z = 1>


