The maximum and minimum of y = sin 2x + 2sinx + 3 (x belongs to R)

The maximum and minimum of y = sin 2x + 2sinx + 3 (x belongs to R)

The original formula can be changed to y = (SiNx + 1) ^ 2 + 2, because x belongs to R, so SiNx can meet positive and negative 1, so when SiNx = 1, there is a maximum value of 6; when SiNx = - 1, there is a minimum value of 2