#NEWLINE# def equation( self , x = 'x' , y = 'y' , z = 'z' , k = 'k' ) : #NEWLINE# #INDENT# "The equation of the line in 3D\n\n        Parameters\n        ==========\n\n        x : str, optional\n            The name to use for the x-axis, default value is 'x'.\n        y : str, optional\n            The name to use for the y-axis, default value is 'y'.\n        z : str, optional\n            The name to use for the x-axis, default value is 'z'.\n\n        Returns\n        =======\n\n        equation : tuple\n\n        Examples\n        ========\n\n        >>> from sympy import Point3D, Line3D\n        >>> p1, p2 = Point3D(1, 0, 0), Point3D(5, 3, 0)\n        >>> l1 = Line3D(p1, p2)\n        >>> l1.equation()\n        (x/4 - 1/4, y/3, zoo*z, k)\n\n        " #NEWLINE# ( x , y , z , k ) = ( _symbol ( x ) , _symbol ( y ) , _symbol ( z ) , _symbol ( k ) ) #NEWLINE# ( p1 , p2 ) = self . points #NEWLINE# a = p1 . direction_ratio ( p2 ) #NEWLINE# return ( ( ( y - p1 . x ) / a [ 0 ] ) , ( ( y - p1 . y ) / a [ 1 ] ) , ( ( z - p1 . z ) / a [ 2 ] ) , k )