cos2xÓëcosx¡¢sinxµÄ¹ØϵÊÇʲô?

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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