Continuity and
Differentiability
Continuous Function
Continuity
A function is continuous at a fixed
point if we can draw the graph of
the function around that point
without lifting the pen from the
plane of the paper.
Continuity of the Function
Discontinuity of the Function
 Graph of the function
cannot be drawn without
lifting the pen.
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CALCULUS
Simple limit problems
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CALCULUS
Trigonometric limits
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Differentiation
 y changes with respect to the change in
the independent input x. This rate of
change is called the derivative of y with
respDifferentiation is a method to
compute the rate at which a dependent
output ect to x.
 The process of finding a derivative is
called differentiation
 We also use the phrase differentiate f (x)
with respect to x to mean find f ′(x).
Derivatives
 The derivative is a measure of how a function changes
as its input changes
 a derivative can be thought of as how much one quantity
is changing in response to changes in some other
quantity
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CALCULUS
Derivatives of exponential functions
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Problem
Differentiation & Integration
 The process of finding a derivative is called
differentiation
 Reverse process of differentiation is called
antidifferentiation.
 Antidifferentiation is the same as integration
 Differentiation and integration constitute the two
fundamental operations in single-variable calculus.
Differentiation from
first Principles
Differentiating a linear function
 Consider the straight line y = 3x + 2
Differentiation from first
principles
 Differentiating a linear function
 Consider the straight line y = 3x + 2
The gradient of the straight line is the same
as the rate of change of y with respect to x.
Differentiation of y = 𝒙 𝟐
 The graph of y = 𝑥2
 P is the point (x, y).
 Q is a nearby point.
 is a small increment in x.
 change in y is written as
 Coordinates of Q are
Differentiation of y = 𝒙 𝟐
Differentiating f(x) = sin x
The derivative of f(x) = cos x.
Derivatives of certain Functions
 The following table gives a list of derivatives of certain
standard functions.
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CALCULUS
Derivatives of trigonometric functions
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Derivatives of Composite
Function
 Eg. f (x) = 2𝑥 + 1 3
 Solution
Rules of Derivatives
 (u ± v)′ = u′ ± v′
 (uv)′ = u′v+ uv′ (Leibnitz or product rule)

𝑢
𝑣
’=
𝑢′ 𝑣 −𝑣′ 𝑢
𝑣2 , wherever v ≠ 0
(Quotientrule).
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Chain Rule
 Let f be a real valued function
 Which is a composite of two functions u and v
 Suppose t = u(x) Suppose t = u(x) and if both
dt
dx
and
dv
dt
exist
then
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CALCULUS
Chain Rule problems
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Explicit and Implicit Function
 y = 𝑓(𝑥) is not given directly
 Explicit Function
 x - y - 𝜋 = 0
 It is easy to solve and rewritten as y = x - 𝜋
 Implicit Function
 X + sin xy – y = 0
 It gives function implicitily.
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CALCULUS
Implicit differentiation
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Derivatives of Inverse Trigonometric
Ratios
 f (x) = sin−1
𝑥
 Let y = sin−1 𝑥 then x = sin y
 Differentiating both sides w.r.t. x we get
1 = cos y
𝑑𝑦
𝑑𝑥
⇒
𝑑𝑦
𝑑𝑥
=
1
𝐶𝑜𝑠 𝑦
=
1
1−𝑥2
Derivatives of Inverse Trigonometric
Ratios
 f (x) = tan−1
𝑥
 Then x = tan y
 Differentiating both sides w.r.t. x we get
 1 = sec2 y
dy
dx

dy
dx
=
1
sec2 y
=
1
1+tan2 y
=
1
(1+(tan( tan−1 𝑥)2
Type equation here.
=
1
1+𝑥2
Derivatives of Inverse Trigonometric
Ratios
 Derivatives of other Trigonometric Functions are
tabulated
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CALCULUS
Derivatives of inverse functions
(The Inverse Function Theorem)
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Exponential Function
 Curves gets steeper as the power of x increases.
 Higher the degree greater
is the growth.
 Steeper the curve faster
is the rate of growth.
 Such a faster growth
is Exponential Function.
Differentiation of Exponential and
Logarithmic Function
 If 𝑓(x) = 𝑒 𝑥 then𝑓’(x) = 𝑒 𝑥
 If 𝑓(x) = log x then 𝑓’(x) =
1
𝑥
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CALCULUS
Derivatives of logarithmic functions
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Derivatives of Parametric
Function
 Neither Explicit nor implicit.
 Relation between two variable expressed via third
variable.
Some standard Derivatives
Second Order Derivatives
 The second order derivative is
Rolle’s Theorem
 R is continuous on a,b
 Differentiable such that
 There exists some c in between
 Such that 𝑓’(c)= 0
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Mean Value Theorem
 R is continuous on a,b
 Differentiable such that
 There exists some c in between
 Such that
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Continuity and differentiability