find the angle between the lines whose direction cosines are given by the equations: l+m+n=0 and l2+m2+n2=0

find the angle between the lines whose direction cosines are given by the equations: l+m+n=0 and $l^{2} + m^{2} + n^{2} = 0$

Matching exercise

Match the items on the right to the items on the left.

STEP 1:

STEP 2:

STEP 3:

STEP 4:

STEP 5: