A)sin2x=2sinxcosx=2cosx√(1-cos²x)
sin2x>0
sin2x=2×0.8√(1-0.64)=1.6√0.36=1.6×0.6=0.96
б)cos2x=2cos²x-1=(2×0.64-1)=(1.28-1)=0.28 x∈[0;π/4]
cos2x=-0.28 x∈(π/4;π/2]
в)tg2x=sin2x/cos2x=0.96/0.28=27=24/7 x∈[0;π/4]
tg2x=-24/7 x∈(π/4;π/2]
г)ctg2x=cos2x/sin2x=0.28/0.96=7/24 x∈[0;π/4]
ctg2x=-7/24 x∈(π/4;π/2]