sin5pai/6如何等于sin pai/6
sin(a\uff0dpai)\u7b49\u4e8e\u591a\u5c11 \u5728\u7ebf\u7b49\u89e3:sin(a\uff0dpai)=-sin(pai\uff0da)=-sin(a)
\u7531cos(\u963f\u6cd5\uff09=cos(-\u963f\u6cd5\uff09\u5f97 cos(\u963f\u6cd5-6\u5206\u4e4bpai)=cos(6\u5206\u4e4bpai-\u963f\u6cd5\uff09
cos(2\u5206\u4e4bpai-\u963f\u6cd5\uff09=sin\uff08\u963f\u6cd5\uff09 \u4e146\u5206\u4e4bpai-\u963f\u6cd5+\uff08\u963f\u6cd5+3\u5206\u4e4bpai\uff09=2\u5206\u4e4bpai
\u6240\u4ee5cos(6\u5206\u4e4bpai-\u963f\u6cd5\uff09=sin(\u963f\u6cd5+3\u5206\u4e4bpai)\uff1d3\u5206\u4e4b1
\u6545cos(\u963f\u6cd5-6\u5206\u4e4bpai)=3\u5206\u4e4b1
sin(5π/6)=sin[π-(π/6)]=sin(π/6)
根据y=sinx的曲线，可知sin(π-a)=sina
所以，sin5/6π=sin(π-5/6π)=sinπ/6
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绛旓細sin5鍏=sin锛4鍏+鍏锛=sin鍏=0
绛旓細鍥犱负Sina=y/X 5涓岀殑缁堣竟鍦▁杞翠笂锛寉=0 鎵浠ヤ负0
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绛旓細鍥炵瓟锛sin(5娲-a) =sin(娲-a) =sina
绛旓細蟺/5銆傛寮﹀嚱鏁板湪绗竴璞￠檺鏄掑鐨勫洜涓合/5銆sin涓鑸寚姝ｅ鸡銆傚彜浠ｈ鐨勫嬀涓夎偂鍥涘鸡浜斾腑鐨勫鸡锛屽氨鏄洿瑙掍笁瑙掑舰涓殑鏂滆竟锛屽嬀銆佽偂鏄洿瑙掍笁瑙掑舰鐨勪袱鏉＄洿瑙掕竟銆傛寮︽槸鑲′笌寮︾殑姣斾緥锛屼綑寮︽槸浣欎笅鐨勯偅鏉＄洿瑙掕竟涓庡鸡鐨勬瘮渚嬨
绛旓細sin(5蟺/3)=sin(蟺+2蟺/3)=-sin(2蟺/3)=-鈭3/2
