sin(2A+π/6)=4/5,A∈(π/6,π/2),求cos2A的值.请快点,有好评!
已知cos2a=7/8,a属于(π/2,π),求sin(a+π/6)-sin2a的值
已知:tanA+1/tanA=5/2,A∈(π/4,π/2),求cos2A和sin(2A+π/4)的值
若a∈(0,π/2)且sin^2 a+cos2a=1/4,求tan a的值
已知sin(π/6-a)=-3/5,且π/6<a<2π/3,求cos2a的值.
已知sin a+cos a=1/3,a属于(π/2,π),求cos2a
cos2a/sin(a-π/4) =-根号(2)/2,则cosa+sina的值为?
若 cos2a/sin(a-π/4)= -√2/2,求cosa+sina的值.
已知sin(π/4-a)=5/13,a∈(0,π/4),求cos2a/cos(π/4+a)的值
已知tana+cota=5/2,求cos2a和sin(2a+π/4)
数学题在线解答已知tana+cota=5/2,a∈(π/4,π/2),求cos2a和sin(2a+π/4)的值
已知sin(a—π/4)=7倍根号2/10,cos2a=7/25,求sina及tan(a+π/3)的值
问一道数学题,已知sinA=5/13,且A属于(π/2,π),求cos2A,sin2A和sin A/2的值