求证|sinx-siny|=|2sin[(x-y)/2]cos[(x+y)/2]|_其他解答

求证|sinx-siny|=|2sin[(x-y)/2]cos[(x+y)/2]|

人气：324 ℃　时间：2020-01-27 03:28:24

解答

|2sin[(x-y)/2]cos[(x+y)/2]|=I2[sin(x/2)cos(y/2)-sin(y/2)cos(x/2)][cos(x/2)cos(y/2)-sin(x/2)(sin(y/2)]=I2[sin(x/2)cos(x/2)cos²(y/2)-sin²(x/2)sin(y/2)cos(y/2)-cos²(x/2)sin(y/2)cos(y/2)+si...