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Let the function f be holomorphic in the unit disk r<=1, assume there is a polynomial p with positive degree such that pf is real valued. Prove that f is constant,
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ilokb: ½ð±Ò+20, ¡ï¡ï¡ï¡ï¡ï×î¼Ñ´ð°¸ 2014-03-05 06:00:28
ÓÉÓÚp(f)ÔÚ µ¼Êý²»ÎªÁãµÄµØ·½ÊDZ£½ÇÓ³É䣬£¨½âÎöº¯ÊýµÄÐÔÖÊ£©£¬¶øp(f)ÏñÔÚÒ»ÌõÖ±ÏßÉÏ£¬ ËùÒÔ p(f) µ¼Êý´¦´¦ÎªÁã¡£

ÓÉÓÚpÊǶàÏîʽ£¬ p'(f)= (f-a1)*(f-a2)...*(f-an) ( ¿ÉÄÜÓÐÖØ¸ù£¬ µ«ÊDz»¿ÉÔ¼Òò×Ó¶¼ÊÇÒ»´ÎµÄ, ´úÊý»ù±¾¶¨Àí)¡£ Òò´Ë (p(f))'= (f-a1)...(f-an)*f' (¸´ºÏº¯ÊýÇóµ¼).

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Òò´Ë£¬ÔÚÔ²ÅÌÉÏ, Ҫô f(z)=ij¸öa1, Ҫô f'(z)=0. Õâ¶¼±íÃ÷fÊdz£Êý¡£
We_must_know. We_will_know.
3Â¥2014-03-05 00:21:10
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3Â¥: Originally posted by hank612 at 2014-03-05 00:21:10
ÓÉÓÚp(f)ÔÚ µ¼Êý²»ÎªÁãµÄµØ·½ÊDZ£½ÇÓ³É䣬£¨½âÎöº¯ÊýµÄÐÔÖÊ£©£¬¶øp(f)ÏñÔÚÒ»ÌõÖ±ÏßÉÏ£¬ ËùÒÔ p(f) µ¼Êý´¦´¦ÎªÁã¡£

ÓÉÓÚpÊǶàÏîʽ£¬ p'(f)= (f-a1)*(f-a2)...*(f-an) ( ¿ÉÄÜÓÐÖØ¸ù£¬ µ«ÊDz»¿ÉÔ¼Òò×Ó¶¼ÊÇÒ»´ÎµÄ, ´ú ...

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