已知sin(x π/12),x∈(π/2,π),求sin2x,cos2x sin...
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
答:详情>>