s1(t) = 2 * sin(t)
s3(t) = 2 / 3 * sin(3 * t - π / 3)
s(t) = s1(t) + s3(t)
g = If(0 ≤ x ≤ 3, 2)
h = If(3 ≤ x ≤ 6, -1)
p = If(6 ≤ x ≤ 9, 2)
a = Integral(s, 1, 3)
b = Integral(g, 1, 3)
c = 4.9 (slider from 0 to 9, step 0.1)
integraleDeS = Integral(s, 0, c)