Implicit Equation of a Plane
–`n T · (P -  P1) = 0
–               a               x                    x1
–Let`n =  b      P =    y         P1 =   y1
–               c               z                    z1
–Then, the equation of a plane becomes:
–a (x - x1) + b (y - y1) + c (z - z1)  = 0
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–a x + b y + c z + d = 0
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–Thus, the coefficients of x, y, z in a plane equation define the normal.
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P1
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