k = 0.4 (slider from 0 to 5, step 0.1)
f(x) = ℯ^((k * x^(2)))
g(x) = ℯ^(((-k) * x^(2)))
k' = 1.6 (slider from 0 to 5, step 0.1)
h(x) = ℯ^((k' * x^(2)))
l(x) = ℯ^(((-k') * x^(2)))