Question

15/pi*[arcsin(-1/2)+arccos(-√3/2)+2arctg(-√3/3)]

Answer 1

$frac{15}{pi}[arcsin(-frac{1}{2})+arccos(-frac{sqrt3}{2})+2arctg(-frac{sqrt3}{3})]=\frac{15}{pi}[-frac{pi}{6}+frac{5pi}{6}-2(frac{pi}{6})]=-frac{5}{2}+frac{25}{2}-5=10-5=5$