问题
填空题
设△ABC中,tanA+tanB+
|
答案
∵tanA+tanB+
=3
tanAtanB⇒tanA+tanB=3
tanAtanB-3
⇒tan(A+B)=3
=-tanA+tanB 1-tanAtanB
.3
∴A+B=120°;
∵cosAcosB=1-sinAsinB⇒cosAcosB+sinAsinB=1⇒cos(A-B)=1⇒A=B
∴A=B=60°.
故答案为:等边
设△ABC中,tanA+tanB+
|
∵tanA+tanB+
=3
tanAtanB⇒tanA+tanB=3
tanAtanB-3
⇒tan(A+B)=3
=-tanA+tanB 1-tanAtanB
.3
∴A+B=120°;
∵cosAcosB=1-sinAsinB⇒cosAcosB+sinAsinB=1⇒cos(A-B)=1⇒A=B
∴A=B=60°.
故答案为:等边