If `l ,\ m,\n` are three lines such that `l || m\ a n d\ n_|_l ,` prove that `n_|_mdot`

If l,n are three lines such that lm and n perp l prove that n perp m.

If l,m and n are three straight lines such that l||m and l||n then prove that m||n .

Prove that l||m||n

If l,m,n are direction cosines of the line then -l,-m,-n can be

n,l,m are three lines in the same plane.If l intersects m and nllm, then find the relation betweenl and n.

If the direction cosines of a straight line are l,m and n, then prove that l^(2)+m^(2)+n^(2)=1

In a \ /_\A B C , If L\ a n d\ M are points on A B\ a n d\ A C respectively such that L M || B C . Prove that: a r\ (\ /_\L C M)=a r\ (/_\ L B M)

If (l_1, m_1, n_1), (l_2, m_2, n_2)" and "(l_3, m_3, n_3) are the direction cosines of three mutually perpendicular lines, prove that the line whose direction cosines are proportional to (l_1+l_2+l_3,m_1+m_2+m_3,n_1+n_2+n_3) makes equal angles with them,

In a \ A B C , If L\ a n d\ M are points on A B\ a n d\ A C respectively such that L M B Cdot Prove that: a r\ (\ L C M)=a r\ ( L B M)

If l_(1), m_(1), n_(1) and l_(2), m_(2), n_(2) are the direction cosines of two lines and l , m, n are the direction cosines of a line perpendicular to the given two lines, then