y=225/4(sinx)^2+2/cosx=225/[8(1-cosx)]+225/[8(1+cosx)]+2/cosx =225/[8(1-t)]+225/[8(1+t)]+2/t t=cosxx=25(1-t)/16+9(1+t)/16+t=17/8 用柯西不等式：sqrt()是开平方根x*y≥{sqrt[(225/8)(25/16)]+sqrt[(225/8)(9...