Show that the three lines with direction cosines `12/13,-3/13,-4/13,4/13,12/13,3/13,3/13,-4/13,12/13 ` are mutually perpendicular.

Show that the three lines with direction cosines quad (12)/(13),(-3)/(13),(-4)/(13),(4)/(13),(12)/(13),(3)/(13);(3)/(13),(-4)/(13),(12)/(13) are mutually perpendicular.

13/12+14/14=

4/13 + 9/13 + 2/13 = ?/13

Check if lines with direction-cosines : lt (12)/(13) , - (3)/(13) , - (4)/(13) gt , lt (4)/(13) , (12)/(13), (3)/(13) gt , lt (3)/(13) , (4)/(13) , (12)/(13) gt are mutually perpendicular .

Arrange in ascending order: 3/13, 8/13, 6/13, 7/13

13^(4/3)div13^(1/3)

13^3-13^2=

Show by using direction ratios, that the points (2,-4,5), (1,-1,3) and (5,-13,11) are collinear