#1
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1) ¨Ò¡ÃÙ» ÁØÁ ADC = 90° ,ÁØÁ DAC = 30° , ÁØÁ CAB = 45° , ÁØÁ ABC = 30°´éÒ¹ DC ÂÒÇ 10 ˹èÇ ´éÒ¹ BC ÂÒÇ¡Õè˹èÇ 2) ¤èҢͧ tan 15° + tan 22.5°+ cot 15° + cot 22.5° à·èҡѺà·èÒã´ ¢Í¢Íº¾ÃФسÅèǧ˹éÒ¤ÃѺ |
#2
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#3
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$\rm{tan}(15)+\rm{tan}(22.5)+\rm{cot}(22.5)+\rm{cot}(15)$
=$\dfrac{\rm{tan^2}(15)+1}{\rm{tan}(15)}+\dfrac{\rm{tan^2}(22.5)+1}{\rm{tan}(22.5)}$ =$\dfrac{\rm{sec^2}(15)}{\rm{tan}(15)}+\dfrac{\rm{sec^2}(22.5)}{\rm{tan}(22.5)}$ =$2[\dfrac{1}{\rm{sin}(30)}+\dfrac{1}{\rm{sin}(45)}]$ =$4+2\sqrt{2}$ 25 ¸Ñ¹ÇÒ¤Á 2013 20:52 : ¢éͤÇÒÁ¹Õé¶Ù¡á¡éä¢áÅéÇ 1 ¤ÃÑé§, ¤ÃÑé§ÅèÒÊØ´â´Â¤Ø³ Euler-Fermat |
#4
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ÍéÒ§ÍÔ§:
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#5
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