The line of greatest slope on an inclined plane P1 is the line in the plane P1 which is perpendicular to the line of intersection of the plane P1 and a horizontal plane P2.
Assuming the plane 4x−3y+7z=0 to be horizontal, the direction cosines of the line of greatest slope in the plane 2x+y−5z=0 are
a. 113,11−1,111
b. 113,111,11−1
c. 11−3,111,111
d. None of these