已知sina cosa=a,求下列各式的值(1)sina*cosa
来源:学生作业帮助网 编辑:作业帮 时间:2024/09/22 04:25:07
(sinA+cosA)^2=1/4sin^2A+cos^2A+2sinAcosA=1/42sinAcosA=-3/4sinAcosA=-3/8sinAcosA/(sin^2A+cos^2A)=-3/8
tan(π/4+a)=[tanπ/4+tana)/[1-tanπ/4*tana]=2(1+tana)/(1-tana)=2tana=1/31/(2sinacosa+cos²a)=(sin
sina/cosa=tana=2sina=2cosasin²a=4cos²a因为sin²a+cos²a=1所以cos²a=1/5sin²a=
tana=3,得sina/cosa=3sina=3cosa因sin²a+cos²a=1所以有10cos²a=1cos²a=1/101+sinacosa-cos&
sinA/cosA=tanA=2sinA=2cosA代入sin²A+cos²A=1sin²A=4/5cos²A=1/5sinAcosA=2cosA*cosA=2
tana=sina/cosa=1/2,所以cosa=2sina,所以根据sin^2a+cos^2a=1,求出sin,cos
2.2,画个三角就出来了
tana/(tana-1)=-1,tana=1/2sin²a+sinacosa+2=(sin²a+sinacosa)/1+2=(sin²a+sinacosa)/(sin^
(2/3sin^2a-sinacosa+cos^2a)/cos^2a*cos^2a=(2/3tan^2a-tana+1)*cos^2a=5cos^2a/3tana=2sina/cosa=2sin^2a
sin^2a-2sinacosa+3cos^2a=(sin^2a-2sinacosa+3cos^2a)/(sin^2a+cos^2a)=[(tana)^2-2tana+3]/[(tana)^2+1]=
sina/cosa=tana=2cosa=1/2*sina代入恒等式sin²a+cos²a=1sin²a=1/5sinacosa=sina(1/2*sina)=1/2*s
sinacosa=1/2*sin2a=1/2*2tana/(1+tan²a)=tana/(1+tan²a)=2/(1+2²)=2/52sin²a-3sinaco
tan(π/4+a)=[tan(π/4)+tana]/[1-tan(π/4)tana]=(1+tana)/(1-tana)=2tana=1/3sinacosa+cos²a=(sinacosa
tana=sina/cosa=2sina=2*cosa(sina)^2=4(cosa)^2因为(sina)^2+(cosa)^2=1所以(cosa)^2=1/52(sina)^2-sinacosa+(
sina/cosa=tana=2sina=2cosa则sin²a=4cos²a因为sin²a+cos²a=1所以cos²a=1/5sin²a
tanA=2运用公式sin2A=2tanA/(1+tan^2A)=4/5sin^2A=tan^2A/(1+tan^2A)=4/5则sinAcosA=sin2A/2=2/5(sinAcosA-sin^2
sin²a-sinacosa=sinacosa(tana-1)=cos²atana(tana-1)又sin²a+cos²a=cos²a(tan
sin^2a表示(sina)²吧∵sina+cosa=0∴tana=-1∵sin^2a+cos^2a=1∴sin^2a+2sinacosa+cos^2a=(sin^2a+2sinacosa+
sina+cosa=1/2两边平方得sin²a+2sinacosa+cos²a=1/41+2sinacosa=1/4∴sinacosa=-3/8sin³a+cos