# Step function Laplace transform - can someone check my work?

1. Dec 1, 2016

### eehelp150

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1
$3u(t)-3u(t-2)$
$\frac{3}{s}-\frac{e^{-2s}3}{s}$

2
$\frac{5t}{2}u(t)-\frac{5t}{2}u(t-2)$
$\frac{5}{2s^2}-\frac{5e^{-2s}}{2s^2}$

3
I have no idea how to do this one.

2. Dec 1, 2016

### rude man

How about using the (integral) definition of the Laplace transform?
You can use Euler's rule to change the cosine factor to more exponentials, leaving just exponentials in the integrand, then perhaps reverse that to get the real transform.
Don't forget to change the phase angle to radians.