来自邱宝梅的问题
已知Sin(45度-x)=5/13,0
已知Sin(45度-x)=5/13,0
1回答
2020-03-10 20:55
已知Sin(45度-x)=5/13,0
已知Sin(45度-x)=5/13,0
sin[2*(45-x)]=2sin(45-x)cos(45-x)=2*5/13*12/13=120/169=sin(90-2x)
所以cos(2x)=sin(90-2x)=120/169