数理答疑团为你解答,希望对你有所帮助.cos(α-7π/2)+2sin(π-3α)/csc(π+α)+sec(π/2+α）=cosα cos(7π/2) + sinα sin(7π/2) + 2[sinπ cos(3α) - cosπsin(3α)]sin(π+α)+ 1/cos(π/2+α）=cosα cos(π/...