Solution in R? Take a look at the2nd graph, the red one is the right side of the equation, and the blue one for the left hand side. They don't intersect, it means no real solution. sin x + 2sin 2x = 3 + sin 3x

For the1st graph, you will see that it never touches the x-axis . . . . same results. sin x + 2sin 2x - sin 3x - 3 = 0