问题
选择题
若A+B=
|
答案
∵A+B=
π,∴tan(A+B)=5 4
=1,∴tanA+tanB=1-tanA•tanB.tanA +tanB 1-tanA•tanB
则(1+tanA)(1+tanB)=1+tanA+tanB+tanA•tanB=1+(1-tanA•tanB )+tanA•tanB=2,
故选D.
若A+B=
|
∵A+B=
π,∴tan(A+B)=5 4
=1,∴tanA+tanB=1-tanA•tanB.tanA +tanB 1-tanA•tanB
则(1+tanA)(1+tanB)=1+tanA+tanB+tanA•tanB=1+(1-tanA•tanB )+tanA•tanB=2,
故选D.