计算arccos(sin 3π/5)的值

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/29 14:00:14

计算arccos(sin 3π/5)的值

设a=arccos(sin 3π/5)
cosa=cosarccos(sin 3π/5)=sin3π/5=cos(π/2-3π/5)=cos(-π/10)=cosπ/10
所以a=π/10

令 a=arccos(3/5) cos(a)=3/5 所以sin(a)=4/5
所以 sin(2a)=2sin(a)*cos(a)=2*3/5*4/5=24/25