EquationSymbolicSolveRequest[List[Equal[E,Cos[θ]]],List[θ]]Solution[{θ,ExpressionSetPoint[Divide[Sum[Product[180,Divide[Product[PI,ACos[E]],180]],Product[360,PI,&N_1]],PI],False,ReservedReal]}]Solution[{θ,ExpressionSetPoint[Divide[Sum[Negative[Product[180,Divide[Product[PI,ACos[E]],180]]],Product[360,PI,&N_2]],PI],False,ReservedReal]}]EquationSymbolicSolveRequest[List[Equal[E,Cos[θ]]],List[E]]Solution[{E,ExpressionSetPoint[Cos[θ],False,ReservedReal]}]GraphingShow2D[PlotPolar2D[E],PlotPolar2D[Cos[θ]],Options[Option[ArgRangeValue,E,0,2,2],Option[RangeX,-2,2],Option[RangeY,-2,2]]]WorksheetAssign[E,Cos[θ]]Cos[θ]Assign[E,Cos[θ]]