Show that the lines whose direction cosines are given by `l+m+n=0`,
`2mn+3nl-5lm=0` are perpendicular to each other .

Show that the lines whose d.c's are given by l + m + n = 0,2mn + 3nl - 5ln = 0 are perpendicular to each other.

Find the angle between the lines, whose direction cosines are given by the equation 3l+m+5n=0 and 6mn-2nl+5lm=0 .

Find the angle between the lines whose direction cosines are given by the equation 3l + m + 5n = 0 and 6mn - 2nl + 5lm = 0