依据诱导公式: sin(2分之π + α)= cosα sin(2分之π - α) =cos(- α) =cos α
sina/(1+cosa)=2sin(a/2)cos(a/2)/[1+2(cos(a/2)^2-1]=2sin(a/2)cos(a/2)/[2(cos(a/2)^2] =sin(a/2)/cos(a/2)=tan(a/2)
解: sinA/2=±√(1-cosA)/2
原式=-cosa
sin(α+β)=sinαcosβ+cosαsinβ 所以sin(α+α)=sinαcosα+cosαsinα=2sinαcosα 满意望采纳( • ̀ω•́ )✧
sⅰn二分之(A+C)=sin(A/2)cos(C/2)+cos(A/2)sin(C/2)
tan A/2 =(sinA/2)/(cosA/2)=2(sin A/2*cos A/2)/2(cos^2 A/2)= =sinA/[2(cos^2 A/2)-1]+1=sinA/1+cosA sosA=1-2sin^2A/2, 2sin^2A/2=1-sosA sin^2A/2=(1-sosA)/2 , sin A/2 = 根号下1-cosA/2
sin2a=2sina*cosasin²a=cos²a-sin²a=2cos²a-1=1-2sin²a
结果为:-cosa 解题过程如下:sin(-π/2十a) 解:=sin(a-π/2)=sina*cosπ/2-cosa*sinπ/2 代入cosπ/2\ufe660 sinπ/2=1=sin(a-π/2)=-cosa 扩展资料 求三角函数的方法:90°的奇数倍+
二倍角公式 sin2θ=2sinθcosθ