Find the acute angle between the two straight lines whose direction cosines are given by `l+m+n=0` and `l^2+m^2-n^2=0`

Find the angle betwween the two straight lines whose direction l,m,n are given by 2l+2m-n=0 and mn+nl;+lm=0

Find the angle between the line whose direction cosines are given by l+m+n=0 and 2l^(2)+2m^(2)-n^(2)-0

The angle between the lines whose directionn cosines are given by 2l-m+2n=0, lm+mn+nl=0 is

The angle between the lines whose direction cosines are given by 3l+4m+5n=0 , l^(2)+m^(2)-n^(2)=0 is

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

Find the angle between the lines whose direction-cosines are given by : (i) l + m + n = 0, l^(2) + m^(2) - n^(2) = 0 (ii) 2l - m + 2n = 0 , mn + nl + lm = 0 ,

Show that the angle between the straight lines whose direction cosines are given by the equation l+m+n=0 and amn+bnl+clm=0 is pi/3 if 1/a+1/b+1/c=0