化简cos(pai/7)*cos(2pai/7)*cos(4pai/7)
问题描述:
化简cos(pai/7)*cos(2pai/7)*cos(4pai/7)
答
cos(pai/7)*cos(2pai/7)*cos(4pai/7)=8sin(pai/7)cos(pai/7)*cos(2pai/7)*cos(4pai/7)/8sin(pai/7)=4sin2(pai/7)*cos(2pai/7)*cos(4pai/7)/8sin(pai/7)=2sin(4pai/7)*cos(4pai/7)/8sin(pai/7)=sin(8pai/7)/8sin(pai/...