（1）y=sinxcosx+sinx+cosx令t= sinx+cosx=√2sin(x+∏/4),∴t∈[-√2,√2]则,t^2=(sinx+cosx)^2=1+2sinxcosx则,sinxcosx=(t^2-1)/2∴y=t+(t^2-1)/2=(1/2)t^2+t-(1/2)令y=g(t)= (1/2)t^2+t-(1/2),t∈[-√2,√2]对称...