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(B) Let the direction cosines of the line be $(l, m, n)$.Since the line is equally inclined to the coordinate axes,the angles $\alpha, \beta, \gamma$

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$\cos ^{-1}\left(\frac{1}{\sqrt{3}}\right)$

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(B) Let the direction cosines of the line be $(l, m, n)$.Since the line is equally inclined to the coordinate axes,the angles $\alpha, \beta, \gamma$ made by the line with the $x, y, z$ axes respectively are equal,i.e.,$\alpha = \beta = \gamma$.Therefore,the direction cosines are equal: $l = m = n$.We know that the sum of the squares of the direction cosines is $l^2 + m^2 + n^2 = 1$.Substituting $l = m = n$,we get $l^2 + l^2 + l^2 = 1$,which implies $3l^2 = 1$.Thus,$l^2 = \frac{1}{3}$,so $l = \pm \frac{1}{\sqrt{3}}$.The angle $\beta$ made by the line with the $y$-axis is given by $\cos \beta = m = \pm \frac{1}{\sqrt{3}}$.Taking the principal value,$\beta = \cos^{-1}\left(\frac{1}{\sqrt{3}}\right)$.

$A$ straight line is equally inclined to all the three coordinate axes. Then,the angle made by the line with the $y$-axis is

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