函数y=(sin^2+1)(cos^2+3)
问题描述：
函数y=(sin^2+1)(cos^2+3)
函数y=(sin^2+1)(cos^2+3)
的最大值是？
答
y=(sin^2+1)(cos^2+3) =sin^2·cos^2+3sin^2+cos^2+3 =sin^2·cos^2+2sin^2+（sin^2+cos^2）+3=sin^2·cos^2+2sin^2+4, 因为sin^2+cos^2=1,移项,cos^2=1-sin^2=sin^2（1-sin^2）+2sin^2+4= -（sin^2)^2+3sin^2+4即求...