Acute angle between the lines whose slopes are $m_1=2,m_2=\frac{1}{2}$  is $\theta$ then the value of $\tan \theta$ is

$\text{ If }\theta \text{ be the acute angle between two lines having slopes }{m}_1\text{ and }{m}_2\text{ then }\tan \theta =\left|\frac{m_1-m_2}{1+m_1{m}_2}\right|$

Hence, 

$\begin{array}{c}\tan \theta =\left|\frac{2-\frac{1}{2}}{1+1}\right|\\ =\frac{3}{4}\end{array}$

$\text{ Therefore, }\tan \theta =0.75$