A body is projected, making an acute angle with the horizontal. If angle between velocity $\overrightarrow{\mathrm{v}}$ and acceleration  $\overrightarrow{\mathrm{g}}\mathrm{is}\mathrm{\theta }$  then $\mathrm{\theta }$ is given by 

Here velocity is acting upwards when projectile is going upwards and acceleration is downwards. The angle $\mathrm{\theta }$  between $\overrightarrow{\mathrm{v}}\hspace{0.17em}\mathrm{and}\hspace{0.17em}\overrightarrow{\mathrm{a}}$ is more than 0° and less than  180°