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Deffiniation of a Limit
-Let f be a function defined on an open interval containing c (exept possibly at c) and let L be a real number
- means that f(x) can be made to be as close to L as desired by making x sufficiently close to c. In that case, it can be stated that "the limit of f of x, as x approaches c, is L". Note that this statement can be true even if f(c) ≠ L. Indeed, the function f(x) need not even be defined at c.
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commontypes of behaviors associated with the non-exitence of a limit
- 1. f(x) approaches a different number from the right side of c than it approaches from the left side.
- 2. f(x) increases or decreases without bound as x approaches c
- 3. f(x) oscillates between two fixed values as x approaches c
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What are three basic limits
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Properties of limits: Sum or difference
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Properties of limits: Product
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Properties of limits: Quotient
and
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Properties of limits: Power
and
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Limit of a composite Function
If f is continuous at b and lim x→a g(x) = b
then lim x→a f(g(x)) = f (lim x→a g(x)) = f (b).
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Limit of Trigonometric Functions:
find limx→c for sin(x) ; cos (x) ; sin(x)/x ; (1-cos(x))/(x)
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- Substituting 0 for x yields 5/0, which is meaningless; hence, = DNE. (Remember, infinity is not a real number.)
- THIS IS AN ASYMPTOTE, NON-REMOVABLE DISCONTINUITY (numerator ≠ 0 , denominator = 0)
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A stradegy For finding limits
- 1. Learn to recognize which limits can be evaluated by direct substituation
- 2. If the limit of f(x) as x approaches c cannot be evaluated by direct substituaiton, try to find a afunction g that agrees with f for all of x other than x=c
- 3. apply the theorem for removable discontinuities such that; lim x→c f(x) = lim x→c g(x) = g(c)
- 4. use a graph or table to reinforce conclusion
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Functions that agree at all but one point
let c be real and let f(x) = g(x) for all x ≠ c in an open interval containing c
If the limit of g(x) as x approaches c exists, then the limit of f(x) also exists
lim x→c f(x) = lim x→c g(x)
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Definition of Continuity
- 1. f(c) is defined
- 2. lim x→c f(x) exists
- 3.
- continuity on an open interval: a function is continuous on an open interval (a,b) if it is continuous at each point in the interval. A function that is continuous on the entire real line ( , ) is everywhere continuous.
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The existence of a limit
let f be a function and let c and L be real numbers
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Definition of continuity on a closed interval
A function is said to be continuous on [a,b] if and only if
- 1. it is continuous on (a,b),
- 2. it is continuous from the right at a and
- 3. it is continuous from the left at b.
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properties of continuity
1. scalar multiple:
2. sum or difference:
3. Product:
4. quotient:
- 1. scalar multiple: bf
- 2. sum or difference: f (+ - ) g
- 3. Product: fg
- 4. quotient: f/g, if g(c) ≠ 0
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Continuity of a compsoite function
If the function g is continuous at a number a, and f is continuous at g(a), the composite function is also continuous at a.
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intermediate value theorem
If a function f is continuous on a closed interval [a,b], then for every value k between f(a) and f(b) there is a value c between a and b such that f(c) = k.
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definition of infinite limits
We say if we can make f(x) arbitrarily large for all x sufficiently close to x=a, from both sides, without actually letting .
We say if we can make f(x) arbitrarily large and negative for all x sufficiently close to x=a, from both sides, without actually letting .
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Definition of a vertical asymptote
if f(x) approaches infinity (or negative infinity) as x approaches c from the right or the left, then the line x=c is a vertical asymptote of the graph of f
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finding vertical asymptote
- let h and g be continuous on an open interval containing c. If g(c) ≠ 0, h(c) = 0, and there exists an open interval containing c such that g(x) ≠ 0 for all x ≠ c in the interval, then the graph of the function given by:
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- has a vertical asymptote at x = c
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properties of infinite limits: sum or difference
Given the functions and suppose we have,
for some real numbers c and L.
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Properties of Infinite Limits: Product
Given the functions and suppose we have,
for some real numbers c and L. Then,
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Properties of infinite limits: Quotient
Given the functions and suppose we have,
for some real numbers c and L. Then,
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Definition of a tangent line with slope m
also known as the slope of the graph of f at x = a
if f is defined on an open interval containing a, and if the limit: exists, then the lines passing through (a, f(a)) with slpoe m is the tangent line to the graph of f at the point (a, f(a))
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Definition of the derivative of a function
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differentialbility implies continuity
if f is differentiable at x = c, then f is continuous at f = c
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The constant rule of the derivative
the derivative of a constant function is 0. That is, if c is a real number, then
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the power rule of the derivative
if n is a rational number, then the function f(x) = x n is differentialble. For f to be differentiable at x=0 then n must be a number such that x n-1 is defined on the interval containing 0
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The sum and differnece rules of the derivative
- The derivative of the sum of two functions is the sum of the derivatives of the two functions:
- .
- Likewise, the derivative of the difference of two functions is the difference of the derivatives of the two functions.
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the derivative of the sin and cos function
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Alternate limit form of the derivative
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How to find the equation of the tangent line through a point (x1,y1)
find the derivative f'(c) = m = slope
plug m into the point slope formula y-y1=m(x-x1)
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