(1)y=lnu,u=lnt,t=x+2
(2)y=sinu,u=1/(x-1)
(3)y=2^u,u=arctant,t=√x
2、
(1)y=1/cosx,cosx≠0,{x|x≠kπ+π/2,k∈Z
(2)cosx≥0,[2kπ-π/2,2kπ+π/2],k∈Z
(3){x|x>0且x≠1}
(1)y=lnu,u=lnt,t=x+2
(2)y=sinu,u=1/(x-1)
(3)y=2^u,u=arctant,t=√x
2、
(1)y=1/cosx,cosx≠0,{x|x≠kπ+π/2,k∈Z
(2)cosx≥0,[2kπ-π/2,2kπ+π/2],k∈Z
(3){x|x>0且x≠1}