# ඉරට්ටේ හා ඔත්තේ ශ්‍රිත

In mathematics, ඉරට්ටේ ශ්‍රිත හා ඔත්තේ ශ්‍රිත are ශ්‍රිතයs which satisfy particular symmetry relations, with respect to taking additive inverses. They are important in many areas of mathematical analysis, especially the theory of power series and Fourier series. They are named for the parity of the powers of the power functions which satisfy each condition: the function f(x) = xn is an even function if n is an even integer, and it is an odd function if n is an odd integer.

## ඉරට්ටේ ශ්‍රිත ƒ(x) = x2 ඉරට්ටේ ශ්‍රිතයක් සඳහා උදාහරණයකි. ƒ(x) = x3 ඔත්තේ ශ්‍රිතයක් සඳහා උදාහරණයකි.

Let f(x) be a real-valued function of a real variable. Then f is even if the following equation holds for all x in the domain of f:

$f(x)=f(-x).\,$ ජ්‍යාමිතිකව , ඉරට්ටෙ ශ්‍රිතයක ප්‍රස්තාරයසමිමිතික with respect to the y-axis, meaning that its graph remains unchanged after ප්‍රතිබිම්බය about the y-axis.

ඉරට්ටෙ ශ්‍රිත සඳහා උදාහරණ ලෙස |x|, x2, x4, cos(x), and cosh(x).

## ඔත්තේ ශ්‍රිත

Again, let f(x) be a තාත්වික-valued function of a real variable. Then f is odd if the following equation holds for all x in the domain of f:

$-f(x)=f(-x)\,,$ or

$f(x)+f(-x)=0\,.$ Geometrically, the graph of an odd function has rotational symmetry with respect to the origin, meaning that its graph remains unchanged after rotation of 180 degrees about the origin.

Examples of odd functions are x, x3, sin(x), sinh(x), and erf(x).

## සමහර තොරතුරු

Note: A function's being odd or even does not imply differentiability, or even continuity. For example, the Dirichlet function is even, but is nowhere continuous. Properties involving Fourier series, Taylor series, derivatives and so on may only be used when they can be assumed to exist.

### මූලික ගුණ

• The only function which is both even and odd is the constant function which is identically zero (i.e., f(x) = 0 for all x).
• The sum of an even and odd function is neither even nor odd, unless one of the functions is identically zero.
• The sum of two even functions is even, and any constant multiple of an even function is even.
• The sum of two odd functions is odd, and any constant multiple of an odd function is odd.
• The product of two even functions is an even function.
• The product of two odd functions is an even function.
• The product of an even function and an odd function is an odd function.
• The quotient of two even functions is an even function.
• The quotient of two odd functions is an even function.
• The quotient of an even function and an odd function is an odd function.
• The derivative of an even function is odd.
• The derivative of an odd function is even.
• The composition of two even functions is even, and the composition of two odd functions is odd.
• The composition of an even function and an odd function is even.
• The composition of any function with an even function is even (but not vice versa).
• The integral of an odd function from −A to +A is zero (where A is finite, and the function has no vertical asymptotes between −A and A).
• The integral of an even function from −A to +A is twice the integral from 0 to +A (where A is finite, and the function has no vertical asymptotes between −A and A).

### ශ්‍රේණි

• The Maclaurin series of an even function includes only even powers.
• The Maclaurin series of an odd function includes only odd powers.
• The Fourier series of a periodic even function includes only cosine terms.
• The Fourier series of a periodic odd function includes only sine terms.

### වීජීය වියුහය

• Any linear combination of even functions is even, and the even functions form a vector space over the reals. Similarly, any linear combination of odd functions is odd, and the odd functions also form a vector space over the reals. In fact, the vector space of all real-valued functions is the direct sum of the subspaces of even and odd functions. In other words, every function f(x) can be written uniquely as the sum of an even function and an odd function:
$f(x)=f_{\text{even}}(x)+f_{\text{odd}}(x)\,,$ where
$f_{\text{even}}(x)={\frac {f(x)+f(-x)}{2}}$ is even and
$f_{\text{odd}}(x)={\frac {f(x)-f(-x)}{2}}$ is odd.
• The even functions form a commutative algebra over the reals. However, the odd functions do not form an algebra over the reals.

### ප්‍රසංවාද

In signal processing, harmonic distortion occurs when a sine wave signal is multiplied by a non-linear transfer function. The type of harmonics produced depend on the transfer function:

• When the transfer function is even, the resulting signal will consist of only even harmonics of the input sine wave; $2f,4f,6f,\dots \$ • When it is odd, the resulting signal will consist of only odd harmonics of the input sine wave; $1f,3f,5f,\dots \$ • When it is asymmetric, the resulting signal may contain either even or odd harmonics; $1f,2f,3f,\dots \$ 