已知tana=3计算4sina-2cosa/5cosa+3sina

已知tana=3计算4sina-2cosa/5cosa+3sina
已知tana=3计算4sina-2cosa/5cosa+3sina

已知tana=3计算4sina-2cosa/5cosa+3sina
由商数关系可知：tana=sina/cosa.
在式子里都同时除于cosa.
[(4sina/cosa)-(2cosa/cosa)]/[(5cosa/cosa)+(3sina/cosa)]
=(4tana-2)/(5+3tana),在把tana=3代入4tana-2/5+3tana
=(4*3-2)/(5+3*3)
=10/14=5/7