Finding correct degree value

Hi All,

Please review the enclosed plot of 3 waves of Sin(theta * degree) plotted against degrees.

I have also plotted a bold black vertical line that intersects all 3 sin plots at approximat 51.4285 degrees.

This does look close, but I am trying to setup a solve to confirm this exact value.

I have tried but I cannot seem to get sensible results.

Please could any one show me how to find the exact value (in degrees) of the vertical black line intersection.

Many thanks for your help & attention,

Best regards,

Lea...