Problem: If a=21β and (a+1)(b+1)=2, then the radian measure of Arctan a+ Arctan b equals
Answer Choices:
A. 2Οβ
B. 3Οβ
C. 4Οβ
D. 5Οβ
E. 6Οβ
Solution:
Let x=Arctana and y=Arctanb :
β(a+1)(b+1)=2(tanx+1)(tany+1)=2tanx+tany=1βtanxtanytan(x+y)=1βtanxtanytanx+tanyβ=1x+y=4Οβ.β