sin2x等于什么？可以怎么化简呢？ sin2x等于多少？
sin2x+cos2x\u600e\u4e48\u5316\u7b80sin2x+cos2x
= \u221a2\u00b7\u3010cos45\u00b7sin2X + sin45\u00b7cos2X\u3011
= \u221a2\u00b7sin[2X + 45]
\u5bf9\u5427 \u52a0\u6cb9
sin2x=2sinxcosx,
\u8fd9\u5176\u5b9e\u662f\u7531\u4e24\u89d2\u548c\u7684\u6b63\u5f26\u516c\u5f0f
sin\uff08x+y\uff09=sinxcosy+cosxsiny \u5f97\u5230\u3002
\u6b64\u5916\uff0c\u8fd8\u6709\u51e0\u4e2a\u4e09\u89d2\u6052\u7b49\u5f0f\uff1a
cos\uff08x+y\uff09=cosxcosy-sinxsiny
cos\uff08x-y\uff09=cosxcosy+sinxsiny
sin\uff08x-y\uff09=sinxcosy-cosxsiny
tan\uff08x+y\uff09=\uff08tanx+tany\uff09/\uff081-tanxtany\uff09
tan\uff08x-y\uff09=\uff08tanx-tany\uff09/\uff081+tanxtany\uff09
\u60f3\u63a8\u5bfc\u51fa\u5404\u79cd\u4e8c\u500d\u89d2\u516c\u5f0f\uff0c
\u53ea\u9700\u5c06\u548c\u89d2\u516c\u5f0f\u4e2d\u7684y\u66ff\u6362\u4e3ax\u5373\u53ef\u3002
*\u6ce8\u610f\uff1a\u4e24\u89d2\u548c\u5dee\u7684\u6b63\u5207\u516c\u5f0f\u5fc5\u987b\u5728\u7b49\u5f0f\u4e24\u8fb9\u90fd\u6709\u610f\u4e49\u65f6\u65b9\u53ef\u6210\u7acb\u3002
sin（X+Y）=sinXcosY+cosXsinY
令X=Y
那么：sin2X=2sinXcosX
sin2x=2sinxcosx=2tanx/(1+(tanx)^2)
2sinxcos。
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绛旓細sin2x=2sinxcosx銆傚垎鏋愯繃绋嬪涓嬶細sin(伪+尾)=sin伪cos尾+ sin尾cos伪 sin(伪-尾)=sin伪cos尾-sinB*cos伪 鏍规嵁sin(伪+尾)=sin伪cos尾+ sin尾cos伪鍙緱锛歴in2x=sin锛坸+x锛=sinxcosx+sinxcosx=2sinxcosx
绛旓細閭ｄ箞锛sin2X=2sinXcosX
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