Laplace Transform for Functions: 5cos(7t+π/4) and e^(3t)sintcost

In summary, the Laplace transformation for functions ##f(t)## are found by using the identity ##f(t)^{'}=sF(s)+f(0)## and the addition formula for ##\cos(a+b)##. For the given functions, ##5cos(7t+\pi /4)## and ##e^{3t}sintcost##, the Laplace transformations are ##\frac{5s}{s^2+49}## and ##\frac{s+3}{(s-3)^2+1}## respectively.
  • #1
skrat
748
8

Homework Statement


Find Laplace transformation for functions ##f(t)##:
a) ##5cos(7t+\pi /4)##
b) ##e^{3t}sintcost##

Homework Equations


The Attempt at a Solution



a) I know that for ##cos(\omega t)## the laplace is ##\frac{s}{s^2+\omega ^2}## but what can I do with that ##\pi /4## ?

I believe I would have to use this identity ##f(t)^{'}=sF(s)+f(0)## but I don't know how o use it...

Could somebody please show me that?
 
Physics news on Phys.org
  • #2
skrat said:

Homework Statement


Find Laplace transformation for functions ##f(t)##:
a) ##5cos(7t+\pi /4)##
b) ##e^{3t}sintcost##


Homework Equations





The Attempt at a Solution



a) I know that for ##cos(\omega t)## the laplace is ##\frac{s}{s^2+\omega ^2}## but what can I do with that ##\pi /4## ?

I believe I would have to use this identity ##f(t)^{'}=sF(s)+f(0)## but I don't know how o use it...

Could somebody please show me that?

Use the addition formula for ##\cos(a+b)## before taking the transform.
 
  • Like
Likes 1 person
  • #3
OMG, How can I be so stupid! -.-

Thanks LCKurtz!
 

What is Laplace transformation?

Laplace transformation is a mathematical tool used to convert functions from the time domain to the frequency domain. It is particularly useful in solving differential equations and analyzing systems with complex dynamics.

What is the purpose of Laplace transformation?

The purpose of Laplace transformation is to simplify complex mathematical problems involving differential equations by converting them into algebraic equations that can be solved more easily.

What are the applications of Laplace transformation?

Laplace transformation has various applications in fields such as physics, engineering, and economics. It is commonly used in circuit analysis, control systems, signal processing, and probability theory.

How is Laplace transformation calculated?

Laplace transformation is calculated by taking the integral of a function multiplied by an exponential term, with the variable of integration being the complex variable s. This results in a new function in the s-domain, which represents the original function in the frequency domain.

What are the advantages of using Laplace transformation?

The advantages of using Laplace transformation include its ability to simplify complex problems, its usefulness in solving differential equations, and its wide range of applications in various fields. It also allows for easier analysis of systems with complex dynamics and provides insights into the behavior of these systems in the frequency domain.

Similar threads

  • Calculus and Beyond Homework Help
Replies
3
Views
2K
  • Calculus and Beyond Homework Help
Replies
10
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
998
  • Calculus and Beyond Homework Help
Replies
3
Views
798
  • Calculus and Beyond Homework Help
Replies
4
Views
2K
  • Calculus and Beyond Homework Help
Replies
9
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
894
  • Calculus and Beyond Homework Help
Replies
1
Views
784
  • Calculus and Beyond Homework Help
Replies
8
Views
2K
Back
Top