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sinA和sin2A怎么转化

sin2A=sinAcosA+sinAcosA(根据 sin(a+b)=sinacosb+cosasinb) =2sinAcosA 2sin2A=4sinAcosA 希望能帮到你,麻烦点击 好评,祝福你 .

sin2a=2*sina*cosa

sin2A=Sin(A+A) =SinACOSA+COSASinA =2SinACosA 所以2sinA乘以cosA=sin2A

解:原式=2sinacosa+sina=sina(2cosa+1)

tanA=sinA/ cos AtanA=1/cotA(sinA)^2+( cos A)^2=1正弦定理a/sinA=b/sinB=c/sinC余弦定理a^2=b^2+c^2-2bc*cosAb^2=c^2+a^2-2ac*cosBc^2=a^2+b^2-2ab*cosC(1)二倍

1) sin2a=2sinacosa (2) cos2a=2(cosa)^2-1=1-2(sina)^2 (3) tan2a=2tana/[1-(tana)^2] 接下来讲讲推导过程: sin2a=sin(a+a)=sinacosa+cosasina=2sinacosa cos2a=cos(a+a)=cosacosa-sinasina=(cosa)^2-(sina)^2=2(cosa)^2-1 =1-2(sina)^2 tan2a=tan(a+a)=(tana+tana)/(1-tanatana)=2tana/[1-(tana)^2]

有个二倍角公式便是2sinacosa=sin2a,

sin2a=2sinacosa∴sin2a/sina=2cosa

解cos(a-π/4)=cosacosπ/4+sinasinπ/4=√2/2(sina+cosa)=1/4对√2/2(sina+cosa)=1/4两边平方1/2(sina+cosa)=1/16(sina+cosa)=1/8即sina+2sinacosa+cosa=1/8即1+sin2a=1/8sin2a=2sinacosa

cos4a=(cos2a)^2-(sin2a)^2=(1-2sina^2)^2-(sin2a)^2

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