题目应是 sin(π/4+2a)sin(π/4-2a)=1/4,a∈(π/4,π/2),求2sin方a+tana-1/tana-1的值?sin(π/4+2a)sin(π/4-2a)=1/4cos(π/2-π/4-2a)sin(π/4-2a)=1/4cos(π/4-2a)sin(π/4-2a)=1/41/2sin(π/2-4a)=1/4cos4a=1/2∵...