å³è¯
cosξ·f(ξ)+sinξ·f'(ξ)=0æç«
æ以
令F(x)=sinxf(x)æ¾ç¶æ»¡è¶³ç½å°å®ççå2个æ¡ä»¶
F'(X)=cosxf(x)+sinx ·f'(x)
å
F(0)=sin0·f(0)=0
F(Ï/2)=sinÏ/2f(Ï/2)=1Ã0=0
å³F(0)=F(Ï/2)
æ以
ç±ç½å°å®çï¼å¾
åå¨Î¾âï¼0ï¼Ï/2ï¼ä½¿å¾
F'(ξ)=0
å³
cosξ·f(ξ)+sinξ·f'(ξ)=0
两边åä¹ä»¥cosξï¼å¾è¯ã
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