1.求最简形式：sin2x/(1+cos2x）cosx/(1+cosx)sinx/(1-cosx)

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1.求最简形式：sin2x/(1+cos2x）*cosx/(1+cosx)*sinx/(1-cosx)
2.化简：根号（2-sin平方2+cos4)
3.已知4sinx=1+cosx,x≠2kπ+π,k∈Z,则tanx=?
4.已知等腰三角形顶角A的正弦值为5/13,求底角B的余弦
5.已知cos(π+a)=4/5,cos(π/2-a)=3/5,那么点P（cos2a,sin2a)在第几象限?

1,sin2x/(1+cos2x）*cosx/(1+cosx)*sinx/(1-cosx)
=2sinx*cosx/[2(cosx)^2]*(cosx*sinx)/[(1+cosx)(1-cosx)]
=2sinx*cosx/[2(cosx)^2]*(cosx*sinx)/[1-(cosx)^2]
=2sinx*cosx/[2(cosx)^2]*(cosx*sinx)/[(sinx)^2]
=1
2,√[2-(sin2)^2+cos4]
=√[2-(sin2)^2+1-2(sin2)^2]
=√3[1-(sin2)^2]
=√3*|cos2|
=-√3*cos2.(cos20,cosB>0)
sinB-cosB=2√26/13 ,或 sinB-cosB=-2√26/13
cosB=√26/26 ,或 cosB=5√26/26
5,cos(π+a)=4/5,cos(π/2-a)=3/5
cosa=-4/5,sina=3/5
cos2a=2(cosa)^2-1=7/25>0
sin2a=2sina*cosa=-24/25

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