A_1 = 2.1 (slider from -5 to 5)
fr_1 = 3.8 (slider from -5 to 5)
phi_1 = 1 (slider from -5 to 5)
f_1(x) = (A_1 * sin((fr_1 * x) + phi_1))
A_2 = 1 (slider from -5 to 5)
fr_2 = -3.46 (slider from -5 to 5)
phi_2 = 0.7 (slider from -5 to 5)
f_2(x) = (A_2 * sin((fr_2 * x) + phi_2))
ff(x) = f_1(x) + f_2(x)