引用:
原帖由 傑Simon 於 2010-9-21 04:01 PM 發表
For maximum value, this method should be ok, right?
In general, "max. value = 上max / 下min" will not work if top and bottom are not independent.
Even if top and bottom are independent, you need to take care about the sign.
However, there is an alternative way to argue that the max. is 0 in this particular case.
The numerator is non-positive while the denominator is positive. Hence, we can conclude that the fraction is non-positive. Furthermore, we see that the value 0 can be attained (when sin x=1). Therefore, 0 is the maximum value.