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发表于 2-10-2012 11:53 PM
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genji 发表于 2-10-2012 09:24 PM 
prove that :
sin2x(cos4x+cos8x+12x)=cos8x sin6x
很难啊。在哪儿找来的题目啊？我做了很久也做不到。
请问你其他的都做到吗除了12x ?
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发表于 3-10-2012 10:03 AM
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sin2x(cos4x+cos8x+cos12x)
试试用这个做。 |
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发表于 14-11-2012 03:26 AM
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sin2x(cos4x+cos8x+cos12x)<<谢谢，真的是题目有问题，用这个就做到了
再来一题past year:
A triangle PQR has median lines PS, QT and RU. The median lines PS and QT meet at a point G such that PG : GS = 1: h and QG : GT = 1: k.
a) Show that GQ + GR = -2hGP and GP + GR = -2kGQ
b) Deduce that h=k=1/2. Hence, show that the median line PS, QT and RU of the triangle PQR are concurrent at G. |
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发表于 28-3-2013 02:59 PM
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