已知sin(π/4+x)=12/13(π/4

问题描述:

已知sin(π/4+x)=12/13(π/4

cos2x / cos(π/4-x)=cos2x/sin(π/2-π/4+x)
=(cos2x)/sin(π/4+x)
sin(π/4+x)=12/13
cos(π/4+x)=7/13(π/4sin(π/4+x)=12/13cos(π/4+x)=7/13(π/4