Find the angle between the lines whose direction cosines are given by the equations: 2l+2m-n=0 and mn+nl+lm=0

Find the angle between the lines whose direction cosines are given by the equations: $2 l + 2 m - n = 0$ and $m n + n l + l m = 0$

Matching exercise

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

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