nm-2-2011-2012-02-slides.pdf
TRANSCRIPT
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Lesson-2:
Fundamental of
DifferentiationEAS 3102
Surjatin WiriadidjajaDepartment of Aerospace EngineeringUniversiti Putra Malaysia
Semester 2/2011-2012
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p2
Introduction
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p3
Objective
understand the basics of differentiation,
relate the slopes of the secant line and tangentline to the derivative of a function,
find derivatives of polynomial, trigonometric andtranscendental functions,
use rules of differentiation to differentiate functions,
find maxima and minima of a function, and
apply concepts of differentiation to real worldproblems.
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p4
Differentiation
The concepts of differentiation:
the secant line, the slope of a tangent line as a background tosolving nonlinear equations using the Newton-Raphson method,finding maxima and minima of functions as a means ofoptimization, the use of the Taylor series to approximate functions,etc.
The derivative of a function represents the rate of change of avariable with respect to another variable.
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Differentiation (cont)
x
Q
P
f(x)
secant line
tangent
line
Figure 1 Function curve with tangent and secant lines.
)(xf
x
P
Q
a a+h
Figure 2 Calculation of the secant line. h
afhafm
hPQ
)()(lim
0tangent,
Concepts of the secant lineand tangent line (Figure 1).
As Q moves closer and closer to P, thelimiting portion is called the tangent line.The slope of the tangent line then is thelimiting value of as :
aha
afhafmPQ
)(
)()(secant,
h
afhaf )()(
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p6
Differentiation (cont)
Derivative of aFunction
The derivative of a function at isdefined as
hafhafaf
h
)()(lim)(0
ax
afxfaf
ax
)()(lim)(
Other Notations ofDerivativesDerivates can be denoted in several ways.
For the first derivative, the notations are
For the second derivative, the notations are
For the derivative, the notations are
dx
dyandyxf
dx
dxf ,),(),(
2
2
2
2
,),(),( dx
yd
andyxfdx
d
xf
n
nn
n
nn
dx
ydyxf
dx
dxf ,),(),(
)()(
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Differentiation (cont)
Theorems of Differentiation
1 The derivative of a constant is zero. If f(x)=k, where k is a constant.
2 The derivative of f(x)=xn, where n0 is f(x)=nxn-1.
3 The derivative of f(x)=kg(x), where k is a constant is f(x)=kg(x).
4 The derivative of f(x0=u(x)v(x) is f(x)=u(x)v(x).
5 The derivative of f(x)=u(x)v(x) is (Product Rule)
6 The derivative of Is (Quotient Rule)
)()()()()( xudx
dxvxv
dx
dxuxf
)(
)()(
xv
xuxf
2))((
)()()()(
)(xv
xvdx
dxuxu
dx
dxv
xf
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Differentiation (cont)
Chain Rule of Differentiation
Implicit Differentiation
Higher order derivatives
)())(())((( xgxgfxgfdx
d
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Differentiation (cont)
Finding maximum and minimum of a functionLet f(x)be a function in domainD, then
A.f(a)is the maximum of the function if f(x) f(a)for all values ofx in the domainD.
B.f(a)is the minimum of the function iff(a) f(x)for all values ofxin the domainD.
The minimum and maximum of a function are also the critical values of afunction. An extreme value can occur in the interval
at end points
a point in where .
a point in where does not exist.
These critical points can be the local maximas and minimas of thefunction
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Differentiation (cont).
f(x)
x
.
Absolute Minimum
Local Minimum
LocalMinimu
m
Local Maximum
(f (x) does not
exist)
Absolute Maximum
Local
Maximum
c d
maximum
minimum
xFigure 7 Graph illustrating the concepts of maximum and
minimum.
Domain = [c,d]
c d
xxf /1)( )(xf
x
Figure 10 Function that has no maximum or
minimum.
)(xf
)(af
ax
ax
x
Figure 11 Graph demonstrates the concept of a singular point with
discontinuous slope at
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p11
Differentiation ofContinuous Functions
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p12
Objective
derive formulas for approximating the firstderivative of a function,
derive formulas for approximating derivatives from
Taylor series,
derive finite difference approximations for higherorder derivatives, and
use the developed formulas in examples to findderivatives of a function.
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p13
Derivative
The derivative of a function atxis defined as
To be able to find a derivative numerically, one could make a
finitexto give,
There are 3 three such approximations.
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p14
Forward Difference ApproximationThe First Derivative
)(xf
xx
x
x
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NUMERICAL METHODS NM-2-2011/2012-02: Fundamental of Differentiation p15
Backward Difference ApproximationThe First Derivative
)(xf
x
xxx
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THE END