cos(-19π/4)的值

来源:学生作业帮助网 编辑:作业帮 时间:2018/12/19 07:12:15
cos(-19π/4)的值cos(-19π/4)的值cos(-19π/4)的值cos(-19π/4)=cos(19π/4)=cos[4π+3π/4]=cos(3π/4)=cos[π-π/4]=-cos

cos(-19π/4)的值
cos(-19π/4)的值

cos(-19π/4)的值
cos(-19π/4)
=cos(19π/4)
=cos[4π+3π/4]
=cos(3π/4)
=cos[π-π/4]
=-cos(π/4)
=-√2/2

cos(-19π/4)
=cos(19π/4)
=cos(19π/4-4π)
=cos(3π/4)
=cos(π/2+π/4)
=-sinπ/4
=-√2/2.