BC 1 Limits 4 Name: Limits and Continuity The concept of limit allows us to replace our informal definition of continuity with one that is mathematically precise. Definition: A function is continuous at a point x = a in the domain of f if and only if lim x a . xa In the case f is continuous at every point in some set S, we say f is continuous on S. If f is not continuous at x = a, we say the function is discontinuous at x = a. (1) (a) Determine any point(s) of discontinuity (x-values) for each of the following functions. x (b) x x 1 x 2 (c) 2 (2) (3) BC 1 1 g x x x 2 3x 3 x2 9 , x3 Suppose x x 3 . 4, x 3 (a) Show that is discontinuous at x = 3. Justify by checking each of the three conditions in the definition for continuity listed above. (b) How should (3) be defined instead to make continuous at that point? (a) Give an example of a function with a removable discontinuity (i.e., a hole) at x = 2. (b) Lim 4.1 Give an example of a function with a jump discontinuity (i.e., a jump or a break forming two separate sections) at x = 2. (4) (5) (6) (7) BC 1 3ax 7, x 1 Let h x 2 . Find the value(s) of a so that h will be continuous at x a, x 1 x 1 . (Use the definition and limits!) Define the value of g ( 2) so that g will be continuous if g x x 2 3x 10 x2 2 x . 3x 2, x 2 x 2 , use the definition of continuity and limits to determine whether If k x 5, 2 x , x2 or not k is continuous at x = 2. Find each limit. Approximate and guess if necessary. ex sin x (a) lim (b) lim x x x x Lim 4.2 (c) lim x ln x x Intermediate Value Property: A function f satisfies the Intermediate Value Property (IVP) on the interval [a,b] if and only if for each number k between f (a ) and f (b) , there exists a value c [ a, b] such that f (c ) k . (8) Which of the following functions satisfy the IVP on the given interval? a. The function below on [2,3] ? 2 1 b. The function f ( x ) c. Define f on (0,1) by On [2, 0] ? On [0, 3] ? 3 1 on [1,1] ? x On [2,10] ? p 1 if x is rational and x in lowest terms q f ( x) q 0 if x is irrational . 1 3 Does f satisfy the IVP on , . 2 2 The Intermediate Value Theorem: If a function f is continuous on the closed interval [a, b] , then f satisfies the Intermediate Value Property (IVP) on the interval [a,b]. Alternately, If a function f is continuous on the closed interval [a, b] , then for each number k between f (a ) and f (b) , there exists a value c [ a, b] such that f (c ) k . BC 1 Lim 4.3