f(x)=（sin2x-cos2x+1）/2sinx
=(2sinxcosx-1+2sin²x+1)/2sinx
=sinx+cosx (x≠kπ)
=√2sin(x+π/4)
-√2≤f(x)≤√2,且f(x)≠1
值域=[-√2,1)∪(1,√2]