cos2x sinxcosx
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cos2X=(cosX)^2-(sinX)^2=2*(cosX)^2-1=1-2*(sinX)^2 ¼´£ºcos2x=2cosxµÄƽ·½-1=cosxµÄƽ·½-sinxƽ·½=1-2sinxµÄƽ·½ µ¹Êý¹Øϵ£º¢Ù £»¢Ú £»¢Û ÉÌÊý¹Ø...
sinxcosxcos2x(»¯¼ò)ÏêϸµãŶ!
=1/2¡Á£¨2sinxcosx£©cos2x =1/2sin2xcos2x ¶þ±¶½Ç¹«Ê½ =1/4£¨2sin2xcos2x£©=£¨sin4x£©/4
¹ØÓÚÈý½Çº¯ÊýµÄת»» sin2x,cos2x,tan2x.ת»¯sinx,conx...
sin2x=2sinxcosx=¡À2sinx¡Ì(1-cos²x)cos2x=cos²x-sin²x=2cos²x-1tan2x=2tanx/(1-tan²x)
sinxcosxcos2xµÈÓÚ?
sinxcosxcos2x =1/2X(2sinxcosx)cos2x =1/2sin2xcos2x =1/4sin4x
ÇëÎÊsinxcosxcos2xµÄÕýÈ·´ð°¸ÊǶàÉÙ?ÔõôËãµÄ?
»ý»¯ºÍ²î¹«Ê½£ºsinxcosx=-1/2*cos2x*cos0 = -1/2cos2x sinxcosxcos2x = -1/2cos2x*cos2x = -1/2cos2x^2
sin2x,cos2x,tan2x·Ö±ðÊǶàÉÙ?
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sinxcosxcos2xµÈÓÚ¶àÉÙ,ÖмäÊdzËŶ!
sinxcosxcos2x=1/2sin2xcos2x=1/4sin4x
0¡Üx<¦Ð,cos2x=cosxsinx½â·½³Ì
cos2x=cosxsinx cos2x=1/2sin2xËùÒÔsin2x/cos2x=2 tan2x=2 tanx=-1+¸ùºÅ5/2 ËùÒÔx=arctan-1+¸ùºÅ5/2
cos2xµÈÓÚ¶àÉÙsinx
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