Question

If lx+my+nz = d is the general form of the equation of a plane and l, m, n are direction cosines of that plane, then what does d represent?

• A. The normal distance of the plane from the origin
• B. Direction cosine of the z-axis
• C. Direction cosine of the y-axis
• D. Direction cosine of the x-axis

Answer 1

The correct option is A The normal distance of the plane from the origin

The Cartesian equation of a plane in normal form is
lx + my + nz = d
where l, m, n are the direction cosines of the unit vector parallel to the normal to the plane; (x,y,z) are the coordinates of the point on a plane and, ‘d’ is the distance of the plane from the origin.