Question

....acest exercițiu....​

Answer 1

$arctg \: x + arctg \: y = arctg \frac{x + y}{1 + xy}$

$= arctg \frac{ \frac{1}{2} + \frac{1}{4} }{1 + \frac{1}{2} \times \frac{1}{4} } = arctg \frac{ \frac{3}{4} }{ \frac{9}{8} } = arctg \frac{24}{36} = arctg \frac{2}{3}$

$tg(arctg( \frac{2}{3} ) = \frac{2}{3} .$