cos20¼õcos40¼õcos80
»¯¼òcos20¡ã - cos40¡ã - cos80¡ãµÈÓÚ?
cos ¦Á+cos ¦Â=2cos[(¦Á+¦Â)/2]¡¤cos[(¦Á-¦Â)/2]£¬´Ë´¦¿ÉÈÏΪ¦Á=80¡ã£¬¦Â=40¡ã)=cos20¡ã-cos20¡ã =0 ...
cos20 - cos40 - cos80=¶àÉÙ°¡
cos20cos40cos80 ÉÏÏÂͬʱ³ËÒÔ8sin20,µÃ£º =8sin20cos20cos40cos80/(8sin20) =4sin40cos40cos80/(8sin20) =2sin...
cos20 - cos40 - cos80=?Çó¹ý³Ì
½â£ºÓɺͲ»ý¹«Ê½£¬cos 40¡ã +cos 80¡ã =2 cos 60¡ã cos 20¡ã =cos 20¡ã.ËùÒÔ Ôʽ =cos 20¡ã -(cos 40¡ã +cos...
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=cos20-2*cos60cos20 =cos20-2*0.5*cos20(cos60 = 0.5)=0
cos20 - cos40 - cos80
cos 40 = cos(60-20) = cos60*cos20+sin60*sin20 cos 80 = cos(60+20) = cos60*cos20-sin60*sin20 ËùÒÔ ´úÈëÔʽ...
cos20¡ã - cos40¡ã - cos80¡ãµÈÓÚ? °³Ë¼Î¬ºÜ²»Áé»î,²»ËµÃ÷°×...
cos40+cos80=cos(60-20)+cos60+20) =cos60cos20+sin60sin20+cos60cos20-sin60sin20 =2cos60cos20 =2*1/2*cos20 =...
»¯¼òcos20¡ãcos40¡ãcos80¡ã
8sin20) =2sin80cos80/(8sin20) =sin160/(8sin20) =sin20/(8sin20) =1/8....
cos20¡ãcos40¡ãcos80¡ãµÈÓÚ¶àÉÙ?
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cos20'cos40'cos60'cos80'=?
ÉÏÃæ³ËÒÔ2sin20`,ÏÂÃæÔÙ³ýÒÔ2sin20`,È»ºó·Ö×ӾͿÉÒÔÓÃ2±¶½ÇÕýÏÒ¹«Ê½ È»ºóÒÀ´ÎÔÙ³ËÒÔ2,Ö±µ½×îºóÊÇsin160`*cos60`/8sin20`µÃ ...