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Concept of Functions

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Topics

  • Sets and Relations
  • Functions
  • Complex Numbers 33
  • Sequences and Series
    • Concept of Sequences
    • Geometric Progression (G.P.)
    • General Term Or the nth Term of a G.P.
    • Sum of the First n Terms of a G.P.
    • Sum of Infinite Terms of a G. P.
    • Recurring Decimals
    • Harmonic Progression (H. P.)
    • Types of Means
    • Special Series (Sigma Notation)
  • Locus and Straight Line
    • Locus
    • Equation of Locus
    • Line
    • Equations of Lines in Different Forms
    • General Form Of Equation Of Line
  • Determinants
  • Limits
    • Definition of Limit of a Function
    • Algebra of Limits
    • Evaluation of Limits
    • Direct Method
    • Factorization Method
    • Rationalization Method
    • Limits of Exponential and Logarithmic Functions
  • Continuity
    • Continuous and Discontinuous Functions
    • Continuity of a Function at a Point
    • Definition of Continuity
    • Continuity from the Right and from the Left
    • Properties of Continuous Functions
    • Continuity in the Domain of the Function
    • Examples of Continuous Functions Whereever They Are Defined
  • Differentiation
    • The Meaning of Rate of Change
    • Definition of Derivative and Differentiability
    • Derivative by the Method of First Principle
    • Rules of Differentiation (Without Proof)
    • Applications of Derivatives
  • Partition Values
    • Concept of Median
    • Partition Values
    • Quartiles
    • Deciles
    • Percentiles
    • Relations Among Quartiles, Deciles and Percentiles
    • Graphical Location of Partition Values
  • Measures of Dispersion
    • Measures of Dispersion
    • Range of Data
    • Quartile Deviation (Semi - Inter Quartile Range)
    • Variance and Standard Deviation
    • Standard Deviation for Combined Data
    • Coefficient of Variation
  • Skewness
    • Skewness
    • Asymmetric Distribution (Positive Skewness)
    • Asymmetric (Negative Skewness)
    • Measures of Skewness
    • Karl Pearson’S Coefficient of Skewness (Pearsonian Coefficient of Skewness)
    • Features of Pearsonian Coefficient
    • Bowley’s Coefficient of Skewness
  • Bivariate Frequency Distribution and Chi Square Statistic
    • Bivariate Frequency Distribution
    • Classification and Tabulation of Bivariate Data
    • Marginal Frequency Distributions
    • Conditional Frequency Distributions
    • Categorical Variables
    • Contingency Table
    • Chi-Square Statistic ( χ2 )
  • Correlation
    • Correlation
    • Concept of Covariance
    • Properties of Covariance
    • Concept of Correlation Coefficient
    • Scatter Diagram
    • Interpretation of Value of Correlation Coefficient
  • Permutations and Combinations
    • Introduction of Permutations and Combinations
    • Fundamental Principles of Counting
    • Concept of Addition Principle
    • Concept of Multiplication Principle
    • Concept of Factorial Function
    • Permutations
    • Permutations When All Objects Are Distinct
    • Permutations When Repetitions Are Allowed
    • Permutations When All Objects Are Not Distinct
    • Circular Permutations
    • Properties of Permutations
    • Combination
    • Properties of Combinations
  • Probability
  • Linear Inequations
  • Commercial Mathematics
    • Percentage
    • Profit and Loss
    • Simple and Compound Interest (Entrance Exam)
    • Depreciation
    • Partnership
    • Goods and Service Tax (GST)
    • Shares and Dividends
  • Function, Domain, Co-domain, Range
  • Types of function
    1. One-one or One to one or Injective function
    2. Onto or Surjective function
  • Representation of Function
  • Graph of a function
  • Value of funcation
  • Some Basic Functions - Constant Function, Identity function, Power Functions, Polynomial Function, Radical Function, Rational Function, Exponential Function, Logarithmic Function, Trigonometric function

Definition

A relation f from a set A to a set B is said to be a function if every element of set A has one and only one image in set B.

A function which has either R or one of its subsets as its range is called a real valued function. Further, if its domain is also either R or a subset of R, it is called a real function.

Notes

In other words, a function f is a relation from a non-empty set A to a non-empty set B such that the domain of f is A and no two distinct ordered pairs in f  have the same first element. 
If f is a function from A to B and (a, b) ∈ f, then f (a) = b, where b is called the image of a under f and a is called the preimage of b under f.
The function f from A to B is denoted by f: A → B.
A funcion is a connection between 2 sets A and B f: A→B such that
1) All elements in A are associated to some element in B
2) This association is unique, that means one and only one.
Let's try to understand this with a simple anology,

Here, let's say `"X"_1` is a set of all children and `"X"_2` is a set of all womens. And `"X"_1` and `"X"_2` have connection as mother and children. 
So as per the definition there is a connention between 2 sets `"X"_1` and `"X"_2` such that all the elements of `"X"_1` are associated to some element in set `"X"_2` i.e all the childrens are related to a particualr mother, and this association is unique because no one child can have two or more mothers, but a mother can have more than one child. 

Consider the sets D and Y related to each ther as shown, clearly every element in the set D is related to exactly one element in the set Y. So the given relation is a function. f: D → Y.
Here, D is the domain of the function and Y is the co domain of the function.
f(1)= 5
Here, 5 is called the image of 1 under f and 1 is called preimage of 5 under f.
The range of this function is, Range= {2,3,5,7}
The range is a set of real numbers so the function is Real valued function. 

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