推 wyob :了解，感謝 01/17 09:25
我覺得你可以這樣寫
Since f(x)=│x│ is cont. on [-1,1]
By WAT, there exists Pn(x) uniformly conv. to f , where Pn(x) are polynomials
and we find that Pn(x) are differentiable on [-1,1]
and Pn→f uniformly
But the limit of Pn(=f=│x│) is "not" differentiable on [-1,1]
(at x=0 , not diff.)
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