Question

锐角三角形的内角A、B，满足tanA-=tanB，则有(    )

A.sin2A-cosB=0                                B.sin2A+cosB=0

C.sin2A-sinB=0                                 D.sin2A+sinB=0

Answer 1

A

解析：∵tanB==-cot2A,

∴1+tan²B=1+cot²2A=.

又cosB==sin2A.

∴sin2A-cosB=0.