|
| |
The limit of a function |
| The definition of the limit of a function |
| A limit on the left (a left-hand limit) and a limit on the right (a right-hand limit) |
| Continuous function |
| Limits at infinity (or limits of functions as x approaches positive or negative infinity) |
| Infinite limits |
| The limit of a function examples |
| Vertical, horizontal and slant (or oblique) asymptotes |
|
|
| |
|
|
| The definition of the limit of a function |
| The limit of a function is a real number L that f (x) approaches as x approaches a given real number a , written |
|
| if for any e > 0 there is a d ( e ) > 0 such that | f (x) - L | < e whenever | x - a | < d ( e ) . |
| The definition says, no matter how small a positive number e we take, we can find a positive number d such that, for an arbitrary chosen value of x from the interval a - d < x < a + d , the corresponding function's values lie inside the interval | | L - e < f (x) < L + e , | | as shows the right figure. | | That is, the function's values can be made arbitrarily close to the number L by choosing x sufficiently close to a , but not equal to a . | | | |
| Therefore, the number d , that measures the distance between a point x from the point a on the x -axis, depends on the number e that measures the distance between the point f (x) from the point L on the y -axis. |
| Example: Given | | |
| whenever | | |
| A limit is used to examine the behavior of a function near a point but not at the point. The function need not even be defined at the point. |
|
| A limit on the left (a left-hand limit) and a limit on the right (a right-hand limit) |
| The limit of a function where the variable x approaches the point a from the left or, where x is restricted to values less than a , is written |
|
| The limit of a function where the variable x approaches the point a from the right or, where x is restricted to values grater than a , is written |
|
| If a function has both a left-handed limit and a right-handed limit and they are equal, then it has a limit at the point. Thus, if |
|
|
|
| Continuous function |
| A real function y = f (x) is continuous at a point a if it is defined at x = a and |
|
| that is, if for every e > 0 there is a d ( e ) > 0 such that | f (x) - f (a) | < e whenever | x - a | < d ( e ) . |
| Therefore, if a function changes gradually as independent variable changes, so that at every value a , of the independent variable, the difference between f (x) and f (a) approaches zero as x approaches a . |
| A function is said to be continuous if it is continuous at all points. |
|
| Limits at infinity (or limits of functions as x approaches positive or negative infinity) |
| We say that the limit of f(x) as x approaches positive infinity is L and write , |
|
| if for any e > 0 there exists N > 0 such that | f (x) - L | < e for all x > N ( e ) . |
| We say that the limit of f (x) as x approaches negative infinity is L and write , |
|
| if for any e > 0 there exists N > 0 such that | f (x) - L | < e for all x < - N ( e ) . |
|
| Not all functions have real limits as x tends to plus or minus infinity. |
| Thus for example, if f (x) tends to infinity as x tends to infinity we write |
|
| if for every number N > 0 there is a number M > 0 such that f (x) > N whenever x > M(N) . |
|
| Infinite limits |
| We write |
|
| if f (x) can be made arbitrarily large by choosing x sufficiently close but not equal to a . |
| We write |
|
| if f(x) can be made arbitrarily large negative by choosing x sufficiently close but not equal to a . |
|
| The limit of a function examples |
| |
| As x tends to 0 from the right f(x) gets larger in positive sense. Therefore, |
|
|
| Vertical, horizontal and slant (or oblique) asymptotes |
| If a point (x, y) moves along a curve f (x) and then at least one of its coordinates tends to infinity, while the distance between the point and a line tends to zero then, the line is called the asymptote of the curve. |
|
| Vertical asymptote |
| If there exists a number a such that |
|
| then the line x = a is the vertical asymptote. |
|
| Horizontal asymptote |
| If there exists a number c such that |
|
| then the line y = c is the horizontal asymptote. |
|
|
| |
|
|
|
|
| |
|
| Calculus contents B |
|
|
|
| Copyright � 2004 - 2020, Nabla Ltd. All rights reserved. |
Belum ada Komentar untuk "F Tends to Infinity as X Tends to Infinity F is Not Unidformly Continuous"
Posting Komentar