Answer
For $t = 0.02$, $E=-3.074$
For $t = 0.04$, $E=1.174$
For $t = 0.08$, $E=-3.074$
For $t = 0.12$, $E=-3.074$
For $t = 0.14$, $E=1.174$
Work Step by Step
We substitute each of the five values of $t$ in the formula to find the value of E for each value of $t$:
For $t = 0.02$,
$E=3.8 \cos 40\pi(0.02)=3.8\cos 0.8\pi=3.8(-0.8090)=-3.074$
For $t = 0.04$,
$E=3.8 \cos 40\pi(0.04)=3.8\cos 1.6\pi=3.8(0.3090)=1.174$
For $t = 0.08$,
$E=3.8 \cos 40\pi(0.08)=3.8\cos 3.2\pi=3.8(-0.8090)=-3.074$
For $t = 0.12$,
$E=3.8 \cos 40\pi(0.12)=3.8\cos 4.8\pi=3.8(-0.8090)=-3.074$
For $t = 0.14$,
$E=3.8 \cos 40\pi(0.14)=3.8\cos 5.6\pi=3.8(0.3090)=1.174$