Question

2arctg1+3arctg(-1÷√3)

Answer 1

$2arctg1+3arctg(-\frac{1}{\sqrt{3}})=2arctg1-3arctg\frac{\sqrt{3}}{3}=\\=2*\frac{\pi}{4}-3*\frac{\pi}{6}=\frac{\pi}{2}-\frac{\pi}{2}=0$