Here’s how you can use GeoGebra to solve a trigonometric equation. GeoGebra has these trigonometric functions built in: 
sin(x) (sine)         
asin(x) (the inverse function of sine)         
cos(x) (cosine)         
acos(x) (the inverse function of cosine)         
tan(x) (tangent)         
atan(x) (the inverse function of tangent) 
     GeoGebra Instruction 1
CAS     under         View     in         Menu.         Solve GeoGebra     will         not         calculate         it         at         all.         In         that         case,         click         on         the         answer         you         got         and         press         Numeric     Evaluation Note!       CAS     uses                    as         the         name         for         the         arbitrary         integer         in         the         solution         of         a         trigonometric         equation.         In         textbooks,                and                are         also         often         used.