[分析] 複數 與 實數 證明 兩題

[u2150260 (鴻哥)]

1. Find the necessary and sufficient conditions on complex number z and w
   in order that |z+w|=|z|+|w|

2.For any real number z and w ,prove that
     |z|/(1+|z|) + |w|/(1+|w|) ≧ |z+w|/(1+|z+w|)

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