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(C) Let the direction cosines of the line be $(l, m, n)$. Since the length of the line is $l$,the projections of the line on the coordinate axes are g

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$l^2$

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(C) Let the direction cosines of the line be $(l, m, n)$. Since the length of the line is $l$,the projections of the line on the coordinate axes are given by $l_1 = l \cdot |l|$,$l_2 = l \cdot |m|$,and $l_3 = l \cdot |n|$.Squaring these,we get $l_1^2 = l^2 l^2$,$l_2^2 = l^2 m^2$,and $l_3^2 = l^2 n^2$.Adding these equations,we get $l_1^2 + l_2^2 + l_3^2 = l^2 (l^2 + m^2 + n^2)$.Since the sum of the squares of the direction cosines is $l^2 + m^2 + n^2 = 1$,we have $l_1^2 + l_2^2 + l_3^2 = l^2 (1) = l^2$.

If the lengths of projections of a line of length $l$ over the coordinate axes are $l_1, l_2$ and $l_3$ respectively,then $l_1^2+l_2^2+l_3^2$ is equal to

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