根号下大于等于02x-4>=0,x>=24-2x>=0,x<=2同时成立则x=2所以2x-4=0,4-2x=0所以y=0+0+x²=4即x=2，y=4
∫[1/sin²xcos²x]dx =∫[4/(2sinxcosx)²]dx =∫[4/sin²2x]dx =∫2csc²2xd2x =-2∫(-csc²2x)d2x =-2cot2x+C
