2.设arctan1/2=A,arctan1/3=B
tan(arctan1/2 + arctan1/3)= tan(A+B)=( tanA+ tanB)/(1-tanA tanB)
=(1/2+1/3)/(1-1/6)=1
所以arctan1/2 + arctan1/3 = π/4
2.设arctan1/2=A,arctan1/3=B
tan(arctan1/2 + arctan1/3)= tan(A+B)=( tanA+ tanB)/(1-tanA tanB)
=(1/2+1/3)/(1-1/6)=1
所以arctan1/2 + arctan1/3 = π/4