Question

A line makes the same angle $\theta$ with each of the x and z- axis. If the angle $\beta$ which it makes with y- axis, is such that $si{n}^2\beta =3si{n}^2\theta$, then $co{s}^2\theta$ equals

• A. $\frac{3}{5}$
• B. $\frac{1}{5}$
• C. $\frac{2}{3}$
• D. $\frac{2}{5}$

Answer 1

The correct option is A $\frac{3}{5}$

Since we know $co{s}^2\theta +co{s}^2\theta +co{s}^2\beta =1\Rightarrow si{n}^2\theta =\frac{2}{5}$