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)

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/...