y=1/(sin2x+cos2x)
=√2/2*1/(√2/2sin2x+√2/2cos2x)
=√2/2*1/[cos(π/4)sin2x+sin(π/4)cos2x]
=√2/2*1/sin(2x+π/4)
sin(2x+π/4)≠0
2x+π/4≠kπ
2x≠kπ-π/4
x≠kπ/2-π/8