Does this do what you want? (C2) csch(z)^2; (D2) CSCH(z)^2 (C3) subst(z*%i,z,d2); (D3) -CSC(z)^2 (C4) trigrat(d3); (D4) 2/(COS(2*z)-1) (C5) subst(z/%i,z,d4); (D5) 2/(COSH(2*z)-1)