a = 1.2 (slider from -4 to 4, step 0.1)
f1 = 6.1 (slider from 1 to 10, step 0.1)
f2 = 6.7 (slider from 1 to 10, step 0.1)
f(x) = cos((((2 * π) * f1) * x)) + cos((((2 * π) * f2) * x)) + (a * cos((((2 * π) * (f1 + f2) / 2) * x)))
g(x) = (2 * cos((((2 * π) * (f1 - f2) / 2) * x))) + a