Find the angle between the lines whose direction cosine are given by the equation: `"l"-"m"+"n"=0" and l"^2-"m"^2-"n"^2=0`

Explanation

We are given the direction cosines using the equation so we have,


`"l"-"m"+"n"=0" quad ---(1)`


`l"^2-"m"^2-"n"^2=0 quad ---(2)`

Now from equation `(1)`, we get,


`m=l+n`

Putting this value in `(2)`,

`l^2-(l+n)^2-n^2=0`


`rArr l^2-(l^2+2ln+n^2)-n^2=0`


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