 # Beta Function  View Notes

## Beta Gamma Function

Functions are a very important part of Mathematics. A function acts as the link between a set of input and output values, such that if you pass a certain input value through a given function, it will always yield one specific output. Therefore, a function is a special correlation between two data sets. Now, we can have some special types of functions. These functions can act as solutions for integral and differential equations. One such set of functions is Euler's Integral Functions. This group consists of two types, namely gamma and beta function. In this article, we are going to discuss the beta function, its definition, properties, the beta function formula, and some problems based on this topic.

### Definition of Beta Function

We would first like to define the beta function before we proceed with the properties and problems. A beta function is a special kind of function which we classify as the first kind of Euler's integrals. The function has real number domains. We express this function as B(x,y) where x and y are real and greater than 0. The beta function is also symmetric, which means B(x, y) = B(y ,x). The notation used for the beta function is "β". The beta function in calculus forms an association between the input and output sets in integral equations and many more mathematical operations.

### Beta Function Formula

The beta function formula is as follows:

$B(p, q) = \int_{0}^{1} t^{p-1} (1-t)^{q-1} dt$

Here, p and q are greater than 0 and real numbers.

The beta function plays a very important role in calculus as it has a very close relationship with the gamma function. The gamma function itself is a general expression of the factorial function in mathematics. The application of the beta-gamma function lies in the simplification of many complex integral functions into simple integrals containing the beta function.

### Relationship Between Beta and Gamma Functions

The beta-gamma function relationship is as follows:

B(p,q)=(Tp.Tq)/T(p+q)

Here, the gamma function formula is:

$\int_{0}^{\infty} e^{-t} t^{z-1} dt$

The beta function can also find expression as the factorial formula given below:

B(p,q)=[(p−1)!(q−1)!]/(p+q−1)!

Here, p! = p. (p-1). (p-2)… 3. 2. 1

These relationships formed by the beta-gamma function are extremely crucial in solving integrals and beta function problems.

### Beta Function Properties

The following are some useful beta function properties that one should keep in mind:

• The beta function is symmetric which means the order of its parameters does not change the outcome of the operation. In other words, B(p,q)=B(q,p).

• B(p, q+1) = B(p, q). [q/(p+q)].

• B(p+1, q) = B(p, q). [p/(p+q)].

• B (p, q). B (p+q, 1-q) = π/ p sin (πq).

### Incomplete Beta Function

The incomplete beta function is basically the formula expressed in a generalised form. We show it by the following relation:

$B(z:a, b) = \int_{0}^{z} t^{a-1} (1-t)^{b-1}dt$

The notation for the same is Bz(a,b). When we put z = 1, we obtain our normal beta function. Therefore, B(1:a,b) = B(a, b).

The incomplete beta function finds application in physics, calculus, mathematical analysis and many other domains.

### Beta Function Applications

The beta function finds implementation in many areas of science and mathematics. For instance, in string theory, which is a part of complex physics, the function computes and represents the scattering amplitudes of the Regge trajectories. The beta-gamma function duo also has numerous applications in calculus.

Now, the basic concepts are clear, we will look at beta function examples and beta function problems with solutions.

### Solved Examples

Q1. Evaluate the following: $\int_{0}^{1} x^{10} (1-x)^{9}dt$.

Solution:

The given beta function is

$\int_{0}^{1} x^{10} (1-x)^{9}dt$

The above expression can also be as follows:

$\int_{0}^{1} x^{11-1} (1-x)^{10-9}dt$

Now, comparing with the standard beta function.

$B(p, q) = \int_{0}^{1} t^{p-1} (1-t)^{q-1} dt$

So, we can say that p = 11 and q = 10.

Using the factorial formula of beta function we get

B(p,q)=[(p−1)!(q−1)!]/(p+q−1)!

Here, p! = p. (p-1). (p-2)… 3. 2. 1

B(p,q) = (10!.9!)/20!

= 0.0000005413

Therefore, the beta function is 0.0000005413.

Q1. What is a Beta Function?

Answer: There are categories of functions in mathematics known as special functions. These have specific functionality, and we use them in several studies and theories. The beta function is one such special function. Beta is one of the two functions of the Euler integrals, and it is particularly the first one. The Euler integrals find application in the solution of integral and differential equations. The formal definition of the beta function is: it is a special function also known as the first Euler integral with real domains and which is symmetric in nature. The general expression is B(x,y) where x and y are real numbers greater than 0.

Q2. State the Beta Function Formula and a Couple of Applications of the Said Function.

Answer: The beta function formula is as given below:

B(p,q)= ∫01tp-1(1-t)q-1dt, where p, q > 0 and are real numbers.

This formula helps in simplifying complex integrals.

Some applications of the beta function are:

• At an introductory level, the beta and gamma functions find widespread implementation in Mathematics. College-level calculus uses a lot of these functions to simplify the learning of integral and differential equations. These functions act as a solution to complex problems where a chunk of the expression can find expression as one of these two functions.

• In higher-level physics and other sciences, this function plays a crucial role. For example, in the string theory, Regge trajectories have scattering amplitudes which we compute using the beta function.

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