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 (12)/(13),(-3)/(13),(-4)/(13),(12)/(13),(3)/(13),(-4)/(13),(12)/(13) are mutually perpendicular.

Show that the lines with direction cosines ((12)/(13),(-3)/(13),(-4)/(13))and((4)/(13),(12)/(13),(3)/(13)) are perpendicular to each other.

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.

3/13+7/13+1/13

3/13-2/13+5/13 =

4/13+9/13+2/13=-/13

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 .

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