Compare to usual method the advantage of laplace transform in solving the differential equation and explane the laplace transform of the periodic function.


This paper describes the Laplace transform used in work outing the differential equation and the comparing with the other usual methods of work outing the differential equation. The method of Laplace transform has the advantage of straight giving the solution of differential equation with given boundary values without the necessity of first happening the general solution and so measuring from it the arbitrary invariables. Furthermore the ready expression of the Laplace cut down the job of work outing differential equations to mere algebraic use.


Differential equation is an equation which involves differential coefficients or

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derived functions. It may be defined in a more refined manner as an equation that defines a Relationship between a map and one or more derived functions of that map. Let y be some map of the independent variable t. Then following are some differential equations associating Y to one or more of its derived functions.

The equation states that the first derived function of the map Y equals the merchandise of and the map y itself. An extra, inexplicit statement in this differential equation is that the declared relationship holds merely for all T for which both the map and its first derivative are defined. Some other differential equations:

Differential equations arise from many jobs in oscillations of mechanical and electrical systems, bending of beams conductivity of heat, speed of chemical reactions etc. , and as such play a really of import function in all modern scientific and technology surveies. There are many ways of work outing the

differential equation and the most effectual manner is to utilize the Laplace equation because it provides the easy way to work out the differential equation without affecting any long procedure of happening out the complementary map and peculiar integral.

Solution of differential equation:

A solution of a differential equation is a relation between the variables which satisfy the given differential equation. A first order homogenous differential equation involves merely the first derived function of a map and the map itself, with invariables merely as multipliers. The equation is of the signifier and can be solved by the substitutio

The solution which fits a specific physical state of affairs is obtained by replacing the solution into the equation and measuring the assorted invariables by coercing the solution to suit the physical boundary conditions of the job at manus. Substituting gives

The general solution to a differential equation must fulfill both the homogenous and non-homogeneous equations. It is the nature of the homogenous solution that the equation gives a nothing value. If you find a peculiar solution to the non-homogeneous equation, you can add the homogenous solution to that solution and it will still be a solution since its cyberspace consequence will be to add nothing. This does non intend that the homogenous solution adds no significance to the image ; the homogenous portion of the solution for a physical state of affairs helps in the apprehension of the physical system. A solution can be formed as the amount of the homogenous and non-homogeneous solutions, and it will hold a figure of arbitrary ( undetermined ) invariables. Such a solution is called the general solution to the differential equation. For application to a physical job, the invariables must be determined by coercing the solution to suit physical boundary conditions. Once a general solution is formed and so forced to suit the physical boundary conditions, one can be confident that it is the alone solution to the job, as gauranteed by the uniqueness theorem.

Uniqueness theorem:

For the differential equations applicable to physical jobs, it is frequently possible to get down with a general signifier and force that signifier to suit the physical boundary conditions of the job. This sort of attack is made possible by the fact that there is one and merely one solution to the differential equation, i.e. , the solution is alone.

Stated in footings of a first order differential equation, if the job meets the status such that degree Fahrenheit ( x, y ) and the derived function of Y is uninterrupted in a given rectangle of ( x, y ) values, so there is one and merely one solution to the equation which will run into the boundary conditions.

Laplace in work outing differential equation:

The Laplace transform method of work outing differential equations outputs peculiar solutions without the necessity of first happening the general solution and so measuring the arbitrary invariables. This method is in general shorter than the above mentioned methods and is specially used for work outing the additive differential equation with changeless coefficients.

Working process:

  • Take the Laplace transform of both sides of the differential equation utilizing the expression of Laplace and the given initial conditions.
  • Permute the footings with subtraction mark to right.
  • Divide by the coefficient of Y, acquiring y as a known map of s.
  • Decide this map of s into partial fractions and take the reverse transform of both sides.

This gives y as a map of T which is the coveted solution fulfilling the given conditions.

Solving the algebraic equation in the mapped infinite

Back transmutation of the solution into the original infinite.

Figure 1: Schema for work outing differential equations utilizing the Laplace transmutation

Some of the illustrations which demonstrate the usage of the Laplace in work outing the differential equation are as follows:

Example no.1 See the differential equation

with the initial conditions.
Continuing utilizing the stairss given above one has

Measure 1:

Measure 2:

Measure 3: The complex map must be decomposed into partial fractions in order to utilize the tabular arraies of correspondences. This gives

By utilizing the expression of the reverse Laplace transform we can change over these frequence domains back in the clip sphere and hence get the coveted consequence as,

Another illustration of the Laplace affecting trigonometric map is

We want to work out

with initial conditions f ( 0 ) = 0 and f & amp ; premier ; ( 0 ) =0.

We note that

and we get

So this is tantamount to

We deduce

So we apply the Laplace opposite transform and acquire

Periodic maps:

In mathematics, a periodic map is a map that repeats its values in regular intervals or periods. The most of import illustrations are the trigonometric maps, which repeat over intervals of length 2 & A ; pi ; . Periodic maps are used throughout scientific discipline to depict oscillations, moving ridges, and other phenomena that exhibit cyclicity.

A map degree Fahrenheit is said to be periodic if

for all values of ten. The changeless P is called the period, and is required to be nonzero. A map with period P will reiterate on intervals of length P, and these intervals are sometimes besides referred to as periods.

For illustration, the sine map is periodic with period 2 & A ; pi ; , since

for all values of ten. This map repeats on intervals of length 2 & A ; pi ; ( see the graph to the right ) .

Geometrically, a periodic map can be defined as a map whose graph exhibits translational symmetricalness. Specifically, a map degree Fahrenheit is periodic with period P if the graph of degree Fahrenheit is invariant under interlingual rendition in the x-direction by a distance of P. This definition of periodic can be extended to other geometric forms and forms, such as periodic tessellations of the plane.A map that is non periodic is called aperiodic.

Laplace transform of periodic maps:

If map degree Fahrenheit ( T ) is periodic with period P & A ; gt ; 0, so that degree Fahrenheit ( t + P ) = degree Fahrenheit ( T ) , and f1 ( T ) is one period ( i.e. one rhythm ) of the map, so the Laplace of this periodic map is given by

The basic construct of the expression is the Laplace Transform of the periodic map degree Fahrenheit ( T ) with period P, equals the Laplace Transform of one rhythm of the map, divided by ( 1 & A ; minus ; e-sp ) .Laplace transform of some of the common maps like the graph given below is given by

Fig no3: continous graphical map

From the graph, we see that the first period is given by:

and that the period p = 2.



Hence, the Laplace transform of the periodic map, degree Fahrenheit ( T ) is given by:

Other uninterrupted moving ridge signifiers and there Laplace transforms are

This moving ridge is an illustration of the full moving ridge rectification which is obtained by the rectifier used in the electronic instruments.


and the period, P = & A ; pi ; .

So the Laplace Transform of the periodic map is given by:


The cognition of Laplace transform has in recent old ages become an indispensable portion of mathematical background required of applied scientists and scientists. This is because the transform method an easy and effectual agencies for the solution of many jobs originating in technology. The method of Laplace transmutation is turn outing to be the most effectual and easy manner of work outing differential equations and hence it is replacing other methods of solution of the differential equation. The most frequent map encompassed in electronics technology is uninterrupted map and most of the maps are in the clip sphere and we need to change over them in the frequence sphere, this operation is performed magnificently by the Laplace transform and hence its application is farther enlarged utilizing it in the solution of the uninterrupted maps.

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