Laplace Transform Help

  • Thread starter Meadman23
  • Start date
  • #1
44
0

Homework Statement


Find the laplace transform of:

v(t) = sin(7t)u(t-3)

Homework Equations



u(t) is step response


The Attempt at a Solution



I know that taken alone the laplace of:

sin(7t) is 7/(s^2+49)

u(t-3) is (1/s)*(e^-3s)


I don't understand how I would figure out the answer to this problem if I have u(t-3). For some reason, seeing the u(t-3) rather than u(t) is really making things hard to understand since I don't know how u(t-3) would be integrated.


I considered setting t-3 =x which would yield:

v(t) =sin(7x+21)u(x)

v(t) = sin(7x)cos(21) + cos(7x)sin(21)

Laplace = [7*cos(21) + s*sin(21)]/[s^2 + 49]

but I don't know if I'm that's the right answer.
 
Last edited:

Answers and Replies

Related Threads on Laplace Transform Help

  • Last Post
Replies
9
Views
1K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
1
Views
8K
  • Last Post
Replies
24
Views
4K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
4
Views
978
  • Last Post
Replies
1
Views
880
  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
12
Views
2K
  • Last Post
Replies
4
Views
3K
Top