1/4（（sinπ/5）/（sinπ/5））=（1/4sin4π/5）/（sinπ/5）） 等号左边是怎么变成右边的解题过程要非常非常非常非常非常非常非常详细!我数学不好,所以如果用到课本公式请标明.

已知sinα=4/5,求下列三角函数值1）sin（-α）2）sin（π-α）3）sin（π+α）4）sin（2π-α） 化简sin(4π-a)*sin(5π-a)=? 已知sin(x+π/6)=1/4,求sin(5π/6-x)+sin^2(π/3-x) sin（-5π/4）= sin（-19π/6）=?已知[3Sin(π+a)+Cos(π-a)]/4Sin(-a)-Sin(5π/2+a)=2，求tan a sin0=0 sin(1/6π)=1/2sin(1/3π)=√3/2sin(1/2π)=1sin(2/3π)=√3/2sin(5/6π)=1/2sin(π)=0sin(-π)=0sin(-5/6π)=-1/2sin(-2/3π)=-√3/2sin(-1/2π)=-1sin(-1/3π)=-√3/2sin(-1/6π)=-1/2sin(7/6π)=-1/2sin(4/3π)=-√3/2sin(5/3π)=-√3/2sin(11/6π)=-1/ 计算,sin(π/12)-sin(5π/12)+2sin(π/8)sin(3π/8) 已知sinα（x+π/6）=1/4,则sin（5π/6-x）+sin（π/3-x）的平方=? 已知sin(x+π/6)=1/4,求sin(5π/6-x)+sin^2（11π/6-x）如题, 比较sin(-27π/5）和sin(43π/4) （二倍角的三角函数）cosπ/5cos2/5π的值是______cosπ/5cos2π/5 =sinπ/5cosπ/5cos2π/5/sinπ/5 =4sinπ/5cosπ/5cos2π/5/4sinπ/5 =2sin2π/5cos2π/5/4sinπ/5 =sin4π/5/4sinπ/5 =sin(π-π/5)/4sinπ/5 =(1/4)sinπ/5/sinπ/5 =1/4但从4sinπ sin(α-β)sin(β-r)-cos(α-β)cos(r-β) 1.sin(α-β)sin(β-r)-cos(α-β)cos(r-β)2.（ tan4分之5π+tan12分之5π）/（1-tan12分之5π）3.[ sin（α+β）-2sinαcosβ]/2sinαsinβ+cos（α+β） 已知sinα=4/5,且3π/2＜α＜2π,求sinα-cosα及（1/cos²α）-（1/sin²α)刚才有些错误，sinα+cosα=4/5 三角函数求解!难题我采纳!10.化简.（1）【sin(2π-α)cos([π/2]+α)cos([π/2]-α)】/【sin(3π-α)sin(-π-α)sin([π/2]+α)】（2）【an(2π-θ)sin(2π-θ)cos(6π-θ)】/【(-cosθ)sin(5π+θ)】11.已知tanα=-2,求sin^2α-4sinαcos 已知sin(π/2-x)+sin(π-x)/cos(-x)+sin(2π-x)=2009,则tan(x+5π/4)等于?已知sin(π/2-x)+sin(π-x)/cos(-x)+sin(2π-x)=2009,则tan(x+5π/4)等于（） A.-2009 B.-1/2009 C.1/2009 D.2009 若sinα-cosα=-1/5,α∈(3/2π,7/4π),求sinα与cosα 若sin（α+β）=1/2,sin(α-β)=1/3,求log√5（ta若sinα-cosα=-1/5,α∈(3/2π,7/4π),求sinα与cosα 若sin（α+β）=1/2,sin(α-β)=1/3,求log√5（tan*cotβ）若sinα-2cosα/3sinα+5 sin（-π/3）+2sin（5π/3)+3sin(2π/3)的值为多少 已知sin(x+π/6)=1/3,求sin(5π/6-x)+sin^2(π/3-x)