For I(t) equal to 2t1/3, build the integral by setting t as the base
and raising this base to the power of (1/3 + 1) or 4/3.
Next write t4/3 and add the given coefficient of 2 to obtain 2t4/3.
Then stick another coefficient of 3/4 between the 2 and the t
to gain 2(3/4)t4/3 or 1.5t4/3.
Now differentiate 1.5t4/3 to confirm that d(1.5t4/3)/dt goes to
(4/3) × (1.5) × t(4/3 − 3/3) or (6/3)t(1/3) or 2t1/3.
∫(from 0 to 1)2t1/3dt evaluates to [1.5t4/3(from 0 to 1)] or
1.5(1)4/3 − 1.5(0)4/3 or 1.5.
∫(from 1 to 3)2t1/3dt evaluates to [1.5t4/3(from 1 to 3)] or
1.5(3)4/3 − 1.5(1)4/3 or 1.5×3×31/3 − 1.5×1×11/3;
a calculator will crush this last down to 4.5×1.44224957 − 1.5
or 4.990123065.