f(x)=sin(wx+φ)+cos(wx+φ)
=√2*(√2/2)*sin(wx+φ)+√2*(√2/2)*cos(wx+φ)
=√2sin(wx+φ)cosπ/4+√2cos(wx+φ)sinπ/4
=√2[sin(wx+φ)cosπ/4+cos(wx+φ)sinπ/4]
=√2sin(wx+φ+π/4)