sin 2b 2sinasinc
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sinƽ·½B=2sinAsinC=2sinBsin£¨¦Ð-2B£©sinB=2sin2B=4sinBcosB cosB=1/4 2 B=90¡ãÇÒa=¸ùºÅ2 £¬´ËʱA+C=90¡ã sinA=cosC sinƽ·½B=2sinAsinC ¿ÉµÃµ½ ...
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sin^2B=sinAsinC.A,CÖÐÓиöÊÇÖ±½Ç.ÉèA=90¶È.sin^2B=sinC,Á½±ß¶¼ÊÇСÓÚ1µÄÕýÊý,ÔòsinB>sinC,B>C,C×îС.sin^2B=sinC=sin(90-B)=cosB cos^2B+sin^2B=cos^...
ÔÚÈý½ÇÐÎABCÖÐ sin^2B=sinasinc ÇÒa^2=c(a+c - b)Çóc/b...
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ÔòS=\frac{1}{2}absinC=\frac{1}{2}\cdot2RsinA\cdot2RsinB\cdot sinC\RightarrowsinAsinBsinC=\frac{S}{2R^2}¹Ì¶¨Íâ½ÓÔ²Ö±¾¶2R£¬Ôò...
ÔÚÈý½ÇÐÎABCÖÐ,ÇóÖ¤sin2A+ sin2B+ sin2C=4 sinA sinB...
sin2A+ sin2B+ sin2C=4 sinA sinB sinC ɨÂëÏÂÔØ×÷Òµ°ïËÑË÷´ðÒÉÒ»ËѼ´µÃ ´ð°¸½âÎö ²é¿´¸ü¶àÓÅÖʽâÎö ½â´ðÒ» ¾Ù±¨ ×óʽ:sin2A+ sin2B+ sin2C=sin2A+ sin2B+sin(2ÅÉ-2A-...
...B,CµÄ¶Ô±ß,ÇÒsin2A+sin2C - sin2B=sinAsinC.(1)Çó½ÇB...
½â´ð:½â:(1)¡ßsin2A+sin2C-sin2B=sinAsinC,¡à¸ù¾ÝÕýÏÒ¶¨Àí,µÃa2+c2-b2=acÒò´Ë,cosB=a2+c2-b22ac=12¡ßB¡Ê(0,¦Ð),¡àB=...
sinB=2sinAsinC,Èôa=b,ÇócosB¡£
2017-03-12 ÔÚÈý½ÇÐÎABCÖÐ,3sinB^2+7sinC^2=2sinA... 2014-06-09 ÒÑÖªÈý½ÇÐÎABCÄÚ½ÇABCÂú×ãsinB=1/2(... 2016-09-28 b c=2acosb...
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sin(2A)=2sinAcosA cos(2A)=cos^{2}A-sin^{2}Atan(2A)=2tanA/(1-tan^{2}A) ´ËÍâ,ÀûÓà cos^{2}A+sin^{2}A=1 ºÍcos(2A)=cos^{2}A-sin^{2}A...sinA/a=sinB/b=sinC/c »òÕßa/sinA=b/sinB=c/sinCÕâÌõ¶¨Àí·Ç³£ÈÝÒ×Ö¤Ã÷,Ö»Òª´Óÿ¸ö¶¥µãÏò¶Ô±ßÒý´¹Ïß,È»ºóÓÃÃæ»ý¹«Ê½:S¡÷ABC=(a*b*sinC)/2=(b*c*sinA)/2=(a*c*sinB)/...
ÔÚÈý½ÇÐÎÄÚ,ʲôÇé¿öÏÂsin A=2sinBsinC?
µ±1-sin2B=0ʱ£¬ tanA(1-sin2B)=1-cos2B B=¦Ð/4+k¦Ð¡£ÒòΪÊÇÈý½ÇÐÎ k=0 B=¦Ð/4 sinA=2sinBsin(A+B) °ÑB=¦Ð/4´øÈë sinA...
ÒÑÖªsin^2B=sinAsinC,Çó½ÇBµÄ·¶Î§
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