已知sin(x+π/12),x∈(π/2,π),求sin2x,cos2x sin(x+π/12)=3/5

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已知sin(x+π/12),x∈(π/2,π),求sin2x,cos2x sin(x+π/12)=3/5
已知sin(x+π/12),x∈(π/2,π),求sin2x,cos2x
sin(x+π/12)=3/5

已知sin(x+π/12),x∈(π/2,π),求sin2x,cos2x sin(x+π/12)=3/5
sin(x+π/12)=3/5,cos(x+π/12)=-4/5
sin2(x+π/12)
=2sin(x+π/12)cos(x+π/12)
=-24/25
sin2(x+π/12)
=sin(2x+π/6)
=√3/2sin2x+1/2cos2x
=-24/25
cos2(x+π/12)
=√3/2cos2x-1/2sin2x
=7/25
sin2x=
cos2x=
接下来自己算