a为第三象限角,sina（2）已知tana=3，求4sina－2cosa/5cosa+3sina的值（2）已知tana=3，求4sina－2cosa/5cosa+3sina的值(2)
(4sina-2cosa)/(5cosa+3sina)
=(4tana-2)/(5+3tana)
=(4×3-2)/(5+3×3)
=5/7