a属于(0,π/2)且tan(a+π/4)=2则lg(sina+2cosa)-lg(sina+3cosa)=?
来源:学生作业帮 编辑:神马作文网作业帮 分类:数学作业 时间:2024/09/20 14:37:42
a属于(0,π/2)且tan(a+π/4)=2则lg(sina+2cosa)-lg(sina+3cosa)=?
RT
RT
/>tan(a+π/4)=(tana+tanπ/4)/(1-tana*tanπ/4)=(tana+1)/(1-tana*1)=2
解得tana=1/3
lg(sina+2cosa)-lg(sina+3cosa)
=lg[(sina+2cosa)/(sina+3cosa)]
=lg[(sina+3cosa-cosa)/(sina+3cosa)]
=lg[1-cosa/(sina+3cosa)]
=lg[1-1/(tana+3)]
把tana=1/3代入,得原式=lg(7/10)=lg7-lg10=lg7-1
解得tana=1/3
lg(sina+2cosa)-lg(sina+3cosa)
=lg[(sina+2cosa)/(sina+3cosa)]
=lg[(sina+3cosa-cosa)/(sina+3cosa)]
=lg[1-cosa/(sina+3cosa)]
=lg[1-1/(tana+3)]
把tana=1/3代入,得原式=lg(7/10)=lg7-lg10=lg7-1
已知tan(a+π/4)=-3,则2sina-cosa/sina+cosa的值是多少?怎么算?
若A属于(-π/2,0),且sinA+cosA=7/13,则(5sina+cosA)/(15sinA-7cosA)=
sina-cosa=1/2,a属于(0,π),则sina+cosa
证明(1-cos^2a)/(sina+cosa)-(sina+cosa)/(tan^2a-1)=sina+cosa
已知a属于(0,π/2),且sina+cosa=tana-1/tana求sina乘cosa的值
证明(1-cos^2a)/(sina-cosa)-(sina+cosa)/(tan^2-1)=sina+cosa
已知tan(π-a)=2分之1,则2sina-cosa分之sina+cosa=
已知sina-cosa=1/5,且a属于(0,π/2) (1)求sina和cosa的值 (2)求cos(2a-π/4)的
已知函数y=tan+cosa/sina,a属于(0,π/2),求y的最小值
sina+cosa=-3/根号5,且|Sina|>|cos a|,求tan(a/2)
tan(a+π/4)=-1/2,求2cosa(sina-cosa)/(1+ tana)
1`已知sina+cosa=2/3,a属于(0,派)求sina,cosa的值