显然sinπ/4=cosπ/4=√2 /2那么sin2x +cos2x=√2 * (sin2x *√2/2+cos2x *√2/2)=√2 * (sin2x *cosπ/4+cos2x *sinπ/4)那么由公式sin(a+b)=sina*cosb +cosa *sinb可以知道,sin2x *cosπ/4+cos2x *sinπ/4=sin(2x+...