Question

已知X不等于kx(k属于Z),函数y=sin^2x+4/sin^2x的最小值是多少?

Answer 1

sin^2x+4/sin^2x=(sin^2x+1/sin^2x)+3/sin^2x≥(2sinx*1/sinx)+3/sin^2x≥2+3=5

故：最小值是5