We need to recall that tan(x) = sin(x)/cos(x) tan(x) is undefinex where cos(x)=0 To answer the question we need to find those x where cos(x)=0 cos(3pi/2)= 0 cos(0)=1 cos(pi/2)=0 cos(pi)=-1
The values for this question are 3pi/2 and pi/2. But for every value that is equal to kpi/2 where k is an even number cos(kpi/2) will be equal to 0;