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INTERPOLATION
INTERPOLATION FOR UNEQUAL INTERVALS
 LAGRANGE’S INTERPOLATING
FORMULA
 Let y = f(x) be the given function
 Let 𝑦0, 𝑦1, … 𝑦𝑛 be the (𝑛 + 1) points of the
given function corresponding to 𝑥0, 𝑥1, … 𝑥 𝑛
 The polynomial 𝑦 = 𝑓 𝑥 can be written as
 𝑓 𝑥 =
𝑥−𝑥1 𝑥−𝑥2 ··· 𝑥−𝑥 𝑛
𝑥0−𝑥1 𝑥0−𝑥2 ··· 𝑥0−𝑥 𝑛
𝑦0 +
𝑥 − 𝑥0 𝑥 − 𝑥2 ··· 𝑥 − 𝑥 𝑛
𝑥1 − 𝑥0 𝑥1 − 𝑥2 ··· 𝑥1 − 𝑥 𝑛
𝑦1 +
𝑥 − 𝑥0 𝑥 − 𝑥1 ··· 𝑥 − 𝑥 𝑛
𝑥2 − 𝑥0 𝑥2 − 𝑥1 ··· 𝑥2 − 𝑥 𝑛
𝑦2
+ ⋯ +
𝑥−𝑥0 𝑥−𝑥1 ··· 𝑥−𝑥 𝑛−1
𝑥 𝑛−𝑥0 𝑥 𝑛−𝑥1 ··· 𝑥 𝑛−𝑥 𝑛−1
𝑦 𝑛
INVERSE INTERPOLATION
 It is the process of finding a value of x
for the corresponding value of y and
we use Lagrange’s interpolation
formula by taking the independent
variable as y and the dependent
variable as x. It is the inverse process
of direct interpolation in which we find
the values of y corresponding to a
value of x, not present in the table.
INVERSE INTERPOLATION BY LAGRANGE’S
 𝑥 =
𝑦−𝑦1 𝑦−𝑦2 ··· 𝑦−𝑦 𝑛
𝑦0−𝑦1 𝑦0−𝑦2 ··· 𝑦0−𝑦 𝑛
𝑥0 +
𝑦−𝑦0 𝑦−𝑦2 ··· 𝑦−𝑦 𝑛
𝑦1−𝑦0 𝑦1−𝑦2 ··· 𝑦1−𝑦 𝑛
𝑥1 +
⋯
+
𝑦−𝑦0 𝑦−𝑦1 ··· 𝑦−𝑦 𝑛−1
𝑦 𝑛−𝑦 𝑦 𝑛−𝑦1 ··· 𝑦 𝑛−𝑦 𝑛−1
𝑥 𝑛
USE OF LAGRANGIAN
INTERPOLATION
 It is a process of computing
intermediate values of a function from
a given set of tabular values of the
function.
DIVIDED DIFFERENCE
 Let 𝑦 = 𝑓(𝑥) be the given function
which takes the values
f(𝑥0), 𝑓(𝑥1) … 𝑓(𝑥 𝑛) corresponding to
the arguments 𝑥0, 𝑥1, … 𝑥 𝑛
respectively, where the intervals
𝑥1 – 𝑥0 , 𝑥2 − 𝑥1 , … 𝑥 𝑛 – 𝑥 𝑛−1 need not
equal
REPRESENTATION BY DIVIDED DIFFERENCE
TABLE
𝐴𝑟𝑔𝑢𝑚𝑒𝑛𝑡
𝑥
𝐸𝑛𝑡𝑟𝑦
𝑓(𝑥)
𝐹𝑖𝑟𝑠𝑡 𝐷. 𝐷
Δ1 𝑓(𝑥)
𝑆𝑒𝑐𝑜𝑛𝑑 𝐷. 𝐷
Δ1
2
𝑓(𝑥)
𝑇ℎ𝑖𝑟𝑑 𝐷. 𝐷
Δ1
3
𝑓(𝑥)
𝑥0
𝑥1
𝑥2
𝑥3
𝑥4
𝑓(𝑥0)
𝑓 𝑥1
𝑓 𝑥2
𝑓 𝑥3
𝑓(𝑥4)
𝑓 𝑥1 –𝑓 𝑥0
𝑥1 –𝑥0
= 𝑓 𝑥0, 𝑥1
𝑓 𝑥2 –𝑓 𝑥1
𝑥2 –𝑥1
= 𝑓 𝑥1, 𝑥2
𝑓 𝑥3 –𝑓 𝑥2
𝑥3 –𝑥2
= 𝑓 𝑥2, 𝑥3
𝑓 𝑥4 –𝑓 𝑥3
𝑥4 –𝑥3
= 𝑓 𝑥3, 𝑥4
𝑓 𝑥1,𝑥2 −𝑓 𝑥0,𝑥1
𝑥2−𝑥0
=
𝑓(𝑥0, 𝑥1, 𝑥2)
𝑓 𝑥2,𝑥3 −𝑓 𝑥1,𝑥2
𝑥3−𝑥1
=
𝑓(𝑥1, 𝑥2, 𝑥3)
𝑓 𝑥3,𝑥4 −𝑓 𝑥2,𝑥3
𝑥4−𝑥2
=
𝑓(𝑥2, 𝑥3, 𝑥4)
𝑓 𝑥1,𝑥2,𝑥3 −𝑓 𝑥0,𝑥1,𝑥2
x3−𝑥0
=
𝑓(𝑥0, 𝑥1, 𝑥2, 𝑥3)
𝑓 𝑥2,𝑥3,𝑥4 −𝑓 𝑥1,𝑥2,𝑥3
𝑥4−𝑥1
=
𝑓(𝑥1, 𝑥2, 𝑥3, 𝑥4)
PROPERTIES OF DIVIDED DIFFERENCES
 1. The divided differences are
symmetrical in all their arguments, that
is, the value of any difference is
independent of the order of the
arguments.
 2. The divided difference of the product
of a constant and a function is equal to
the product of the constant and the
divided difference of the function.
 3. The operator Δ1 is linear
 4. The 𝑛 𝑡ℎ
divided difference of a
polynomial of degree 𝑛 is a constant
NEWTON DIVIDED DIFFERENCE INTERPOLATION
 If 𝑓(𝑥) is a polynomial of degree𝑛, and
𝑓(𝑥0), 𝑓(𝑥1), … 𝑓(𝑥 𝑛) are the
corresponding values of arguments
𝑥0, 𝑥1, … . 𝑥 𝑛 respectively, not
necessarly equally spaced.
 Then 𝑓 𝑥 = 𝑓 𝑥0 + ( 𝑥 −
INTERPOLATION WITH EQUAL INTERVALS
 FORWARD DIFFERENCE
 If 𝑦0, 𝑦1, … 𝑦𝑛 are the values of 𝑦 = 𝑓(𝑥)
corresponding to the arguments 𝑥0, 𝑥1, … 𝑥 𝑛 ,
where 𝑥1 − 𝑥0 , 𝑥2 − 𝑥1, … 𝑥 𝑛 − 𝑥 𝑛−1 are equal
 𝑖. 𝑒 𝑥𝑖 = 𝑥0 + 𝑖ℎ, 𝑖 = 0,1,2 … 𝑛
 Define Δ𝑦0 = 𝑦1 − 𝑦0 , Δ𝑦1 = 𝑦2 − 𝑦1 … . Δ𝑦 𝑛−1 =
𝑦𝑛 − 𝑦 𝑛−1
 And Δ2
𝑦0 = Δ𝑦1 − Δ𝑦0 , Δ2
𝑦1 = Δ𝑦2 −
Δ𝑦1 … . Δ2
𝑦 𝑛−1 = Δ𝑦𝑛 − Δ𝑦 𝑛−1
 And so on
 Here Δ is called Newton’s forward difference
operator
 NEWTON’S FORWARD
DIFFERENCE FORMULA
 If 𝑦0, 𝑦1, … 𝑦𝑛 are the values of 𝑦 =
𝑓(𝑥) corresponding to the arguments
𝑥0, 𝑥1, … 𝑥 𝑛
 Then y = 𝑦0 + 𝑝∆𝑦0 +
𝑝 𝑝−1
2!
∆2
𝑦0 +
𝑝 𝑝−1 𝑝−2
3!
∆3
𝑦0 + ⋯
 Where 𝑝 =
𝑥−𝑥0
ℎ
.
FORWARD DIFFERENCE
TABLE
𝑥 𝑦 Δ Δ2
Δ3
Δ4
Δ5
𝑥0
𝑥1
𝑥2
𝑥3
𝑥4
𝑥5
𝑦0
𝑦1
𝑦2
𝑦3
𝑦4
𝑦5
Δ𝑦0
Δ𝑦1
Δ𝑦2
Δ𝑦3
Δ𝑦4
Δ2
𝑦0
Δ2
𝑦1
Δ2
𝑦2
Δ2
𝑦3
Δ3
𝑦0
Δ3
𝑦1
Δ3
𝑦2
Δ4
𝑦0
Δ4
𝑦1
Δ5
𝑦0
BACKWARD DIFFERENCE
 The differences 𝑦1 − 𝑦0, 𝑦2 − 𝑦1, … . 𝑦𝑛 −
𝑦 𝑛−1 are called first backward differences
and denoted by
 𝛻𝑦1 = 𝑦1 − 𝑦0, 𝛻𝑦2 = 𝑦2 − 𝑦1, … .
𝛻𝑦𝑛 = 𝑦𝑛 − 𝑦 𝑛−1
 And 𝛻2
𝑦1 = 𝛻𝑦1 − 𝛻𝑦0,
𝛻2
𝑦2 = 𝛻𝑦2 − 𝛻𝑦1, … .
𝛻2
𝑦𝑛 = 𝛻𝑦𝑛 − 𝛻𝑦 𝑛−1
and so on
NEWTON’S BACKWARD DIFFERENCE FORMULA
 If 𝑦0, 𝑦1, … 𝑦𝑛 are the values of 𝑦 =
𝑓(𝑥) corresponding to the arguments
𝑥0, 𝑥1, … 𝑥 𝑛
 Then 𝑦 = 𝑦𝑛 + 𝑝𝛻𝑦𝑛 +
𝑝 𝑝+1
2!
𝛻2
𝑦𝑛 +
𝑝 𝑝+1 𝑝+2
3!
𝛻3
𝑦𝑛 + ⋯
 Where 𝑝 =
𝑥−𝑥 𝑛
ℎ
.
BACKWARD DIFFERENCE
TABLE
𝑥 𝑦 𝛻 𝛻2
𝛻3
𝛻4
𝛻5
𝑥0
𝑥1
𝑥2
𝑥3
𝑥4
𝑥5
𝑦0
𝑦1
𝑦2
𝑦3
𝑦4
𝑦5
𝛻𝑦1
𝛻𝑦2
𝛻𝑦3
𝛻𝑦4
𝛻𝑦5
𝛻2
𝑦2
𝛻2
𝑦3
𝛻2
𝑦4
𝛻2
𝑦5
𝛻3
𝑦3
𝛻3
𝑦4
𝛻3
𝑦5
𝛻4
𝑦4
𝛻4
𝑦5
𝛻5
𝑦5
NUMERICAL
DIFFERENTIATION
DERIVATIVES USING DIVIDED DIFFERENCE
 Procedure
 Step 1. By using Newton’s divided
difference formula find 𝑓(𝑥) in terms of
x
 Step 2. Find the derivatives of 𝑓(𝑥)
DERIVATIVE - USING NEWTON’S FORWARD DIFFERENCE
FORMULA
 The first derivative of y at 𝑥 = 𝑥0 + 𝑝ℎ (near beginning of the data)
is
𝑑𝑦
𝑑𝑥
=
𝑑𝑦
𝑑𝑝
𝑑𝑝
𝑑𝑥

𝑑𝑦
𝑑𝑥
=
1
ℎ
∆𝑦0 +
2𝑝−1
2!
∆2 𝑦0 +
3𝑝2−6𝑝+2
3!
∆3 𝑦0 + ⋯
 The second derivative of y at 𝑥 = 𝑥0 + 𝑝ℎ is
𝑑2 𝑦
𝑑𝑥2 =
𝑑2 𝑦
𝑑𝑝2
𝑑𝑝
𝑑𝑥
2

𝑑2 𝑦
𝑑𝑥2 =
1
ℎ2 ∆2
𝑦0 + (𝑝 − 1)∆3
𝑦0 +
6𝑝2−18𝑝+11
12
∆4
𝑦0 + ⋯
 The third derivative y at 𝑥 = 𝑥0 + 𝑝ℎ

𝑑3 𝑦
𝑑𝑥3 =
1
ℎ3 ∆3
𝑦0 +
12𝑝−18
12
∆4
𝑦0+. .
 For tabular values, at 𝑥 = 𝑥0, (𝑝 = 0)

𝑑𝑦
𝑑𝑥
=
1
ℎ
∆𝑦0 −
∆2 𝑦0
2
+
∆3 𝑦0
3
−
∆4 𝑦0
4
+ ⋯

𝑑2 𝑦
𝑑𝑥2 =
1
ℎ2 ∆2
𝑦0 − ∆3
𝑦0 +
11
12
∆4
𝑦0 − ⋯

𝑑3 𝑦
𝑑𝑥3 =
1
ℎ3 ∆3 𝑦0 −
3
2
∆4 𝑦0+. .
DERIVATIVE - USING NEWTON’S BACKWARD DIFFERENCE
FORMULA
 The first derivative of y at 𝑥 = 𝑥 𝑛 + 𝑝ℎ (near end of the data) is
𝑑𝑦
𝑑𝑥
=
𝑑𝑦
𝑑𝑝
𝑑𝑝
𝑑𝑥

𝑑𝑦
𝑑𝑥
=
1
ℎ
𝛻𝑦 𝑛 +
2𝑝+1
2!
𝛻2 𝑦 𝑛 +
3𝑝2+6𝑝+2
3!
𝛻3 𝑦 𝑛 + ⋯
 The second derivative of y at 𝑥 = 𝑥 𝑛 + 𝑝ℎ is
𝑑2 𝑦
𝑑𝑥2 =
𝑑2 𝑦
𝑑𝑝2
𝑑𝑝
𝑑𝑥
2

𝑑2 𝑦
𝑑𝑥2 =
1
ℎ2 𝛻2
𝑦 𝑛 + (𝑝 + 1)𝛻3
𝑦 𝑛 +
6𝑝2+18𝑝+11
12
𝛻4
𝑦0 + ⋯
 The third derivative of y at 𝑥 = 𝑥 𝑛 + 𝑝ℎ

𝑑3 𝑦
𝑑𝑥3 =
1
ℎ3 𝛻3
𝑦 𝑛 +
12𝑝+18
12
𝛻4
𝑦0+. .
 For tabular values, at 𝑥 = 𝑥 𝑛, (𝑝 = 0)

𝑑𝑦
𝑑𝑥
=
1
ℎ
𝛻𝑦 𝑛 +
𝛻2 𝑦 𝑛
2
+
𝛻3 𝑦 𝑛
3
+ ⋯

𝑑2 𝑦
𝑑𝑥2 =
1
ℎ2 𝛻2
𝑦 𝑛 + 𝛻3
𝑦 𝑛 +
11
12
𝛻4
𝑦0 + ⋯

𝑑3 𝑦
𝑑𝑥3 =
1
ℎ3 𝛻3 𝑦 𝑛 +
3
2
𝛻4 𝑦0+. .
NUMERICAL INTEGRATION
SINGLE (LINEAR) INTEGRATION
1. TRAPEZOIDAL RULE
2. SIMPSON’S
𝟏
𝟑
RULE
TRAPEZOIDAL RULE

𝑥0
𝑥1
𝑓(𝑥) 𝑑𝑥 =
ℎ
2
𝑦0 + 𝑦𝑛 + 2( 𝑦1 + 𝑦2 +
SIMPSON’S
𝟏
𝟑
𝒓𝒅 RULE

𝑥0
𝑥1
𝑓(𝑥) 𝑑𝑥 =
ℎ
3
𝑦0 + 𝑦𝑛 + 4 𝑦1 + 𝑦3 + 𝑦5 + ⋯ + 2(𝑦2 + 𝑦4 + 𝑦6+. . )
=
ℎ
3
𝑓𝑖𝑟𝑠𝑡 + 𝑙𝑎𝑠𝑡 + 4 𝑠𝑢𝑚 𝑜𝑓 𝑜𝑑𝑑 𝑡𝑒𝑟𝑚𝑠 +
2 𝑠𝑢𝑚 𝑜𝑓 𝑒𝑣𝑒𝑛 𝑡𝑒𝑟𝑚𝑠 ]
 ℎ =
𝑥1−𝑥0
𝑛
, 𝑛 − 𝑖𝑠 𝑡ℎ𝑒 𝒆𝒗𝒆𝒏 𝑛𝑜 𝑜𝑓 𝑠𝑢𝑏 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙𝑠 𝑖𝑛 𝑥0 𝑥1
 Condition for applying the Simpson’s rule – Number
of subintervals must be even
NUMERICAL DOUBLE
INTEGRATION
 1. 𝐓𝐑𝐀𝐏𝐄𝐙𝐎𝐈𝐃𝐀𝐋 𝐑𝐔𝐋𝐄
 2. 𝐒𝐈𝐌𝐏𝐒𝐎𝐍’𝐒 𝐑𝐔𝐋𝐄
TRAPEZOIDAL RULE

𝑎
𝑏
𝑐
𝑑
𝑓 𝑥, 𝑦 𝑑𝑥𝑑𝑦 =
ℎ𝑘
4
𝑓1 + 𝑓3 + 𝑓7 + 𝑓9 +
2 𝑓2 + 𝑓4 + 𝑓6 + 𝑓8 + 4𝑓5]
 =
ℎ𝑘
4
𝑆𝑢𝑚 𝑜𝑓 𝑐𝑜𝑟𝑛𝑒𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 +
2 𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑜𝑢𝑛𝑑𝑎𝑟𝑦 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 +
4(𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑖𝑛𝑡𝑒𝑟𝑖𝑜𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓(𝑥, 𝑦)]
y x 𝑥0 𝑥1 𝑥2 𝑥3
𝑦0 𝑓(𝑥0, 𝑦0) 𝑓(𝑥1, 𝑦0) 𝑓(𝑥2, 𝑦0) 𝑓(𝑥3, 𝑦0)
𝑦1 𝑓(𝑥0, 𝑦1) 𝑓(𝑥1, 𝑦1) 𝑓(𝑥2, 𝑦1) 𝑓(𝑥3, 𝑦1)
𝑦2 𝑓(𝑥0, 𝑦2) 𝑓(𝑥1, 𝑦2) 𝑓(𝑥2, 𝑦2) 𝑓(𝑥3, 𝑦2)
𝑦3 𝑓(𝑥0, 𝑦3) 𝑓(𝑥1, 𝑦3) 𝑓(𝑥2, 𝑦3) 𝑓(𝑥3, 𝑦3)
For example, if x takes the values 𝑥0, 𝑥1, 𝑥2, 𝑥3 and y takes values
𝑦0, 𝑦1, 𝑦2, 𝑦3
Red indicates – corner values
Blue indicates – boundary values
Black indicates – interior values
𝑺𝑰𝑴𝑷𝑺𝑶𝑵’𝑺 𝑹𝑼𝑳𝑬

𝑎
𝑏
𝑐
𝑑
𝑓 𝑥, 𝑦 𝑑𝑥𝑑𝑦 =
ℎ𝑘
9
𝑓1 + 𝑓3 + 𝑓7 + 𝑓9 +
2 𝑓2 + 𝑓4 + 𝑓6 + 𝑓8 + 16𝑓5]
 =
ℎ𝑘
9
𝑆𝑢𝑚 𝑜𝑓 𝑐𝑜𝑟𝑛𝑒𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 +
4 𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑜𝑢𝑛𝑑𝑎𝑟𝑦 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 +
16(𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑖𝑛𝑡𝑒𝑟𝑖𝑜𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓(𝑥, 𝑦)]
Errors in Trapezoidal rule of numerical
integration.
 When evaluating 𝑎
𝑏
𝑓 𝑥 𝑑𝑥, the error
in the trapezoidal rule is
 <
𝑏−𝑎 2
12
ℎ2
𝑀, where ℎ =
𝑏−𝑎
𝑛
, n is the
number of subintervals of (a, b),
 And 𝑀 = 𝑚𝑎𝑥{|𝑦0
′′
|, |𝑦1
′′
|,· · ·
, |𝑦 𝑛−1
′′
|}, 𝑦𝑟′′ = 𝑓′′(𝑥 𝑟)
 Error in Trapezoidal rule is of order
𝒉 𝟐
Errors in Simpson’s rule of numerical
integration
 The error in Simpson’s rule is <
𝑏−𝑎
180
ℎ4
𝑀
 where ℎ =
𝑏−𝑎
2𝑛
, 2n is the number of
subintervals of (a, b),
 𝑀 = 𝑚𝑎𝑥 𝑦0
1
, 𝑦1
4
,· · ·

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Interpolation

  • 2. INTERPOLATION FOR UNEQUAL INTERVALS  LAGRANGE’S INTERPOLATING FORMULA  Let y = f(x) be the given function  Let 𝑦0, 𝑦1, … 𝑦𝑛 be the (𝑛 + 1) points of the given function corresponding to 𝑥0, 𝑥1, … 𝑥 𝑛  The polynomial 𝑦 = 𝑓 𝑥 can be written as  𝑓 𝑥 = 𝑥−𝑥1 𝑥−𝑥2 ··· 𝑥−𝑥 𝑛 𝑥0−𝑥1 𝑥0−𝑥2 ··· 𝑥0−𝑥 𝑛 𝑦0 + 𝑥 − 𝑥0 𝑥 − 𝑥2 ··· 𝑥 − 𝑥 𝑛 𝑥1 − 𝑥0 𝑥1 − 𝑥2 ··· 𝑥1 − 𝑥 𝑛 𝑦1 + 𝑥 − 𝑥0 𝑥 − 𝑥1 ··· 𝑥 − 𝑥 𝑛 𝑥2 − 𝑥0 𝑥2 − 𝑥1 ··· 𝑥2 − 𝑥 𝑛 𝑦2 + ⋯ + 𝑥−𝑥0 𝑥−𝑥1 ··· 𝑥−𝑥 𝑛−1 𝑥 𝑛−𝑥0 𝑥 𝑛−𝑥1 ··· 𝑥 𝑛−𝑥 𝑛−1 𝑦 𝑛
  • 3. INVERSE INTERPOLATION  It is the process of finding a value of x for the corresponding value of y and we use Lagrange’s interpolation formula by taking the independent variable as y and the dependent variable as x. It is the inverse process of direct interpolation in which we find the values of y corresponding to a value of x, not present in the table.
  • 4. INVERSE INTERPOLATION BY LAGRANGE’S  𝑥 = 𝑦−𝑦1 𝑦−𝑦2 ··· 𝑦−𝑦 𝑛 𝑦0−𝑦1 𝑦0−𝑦2 ··· 𝑦0−𝑦 𝑛 𝑥0 + 𝑦−𝑦0 𝑦−𝑦2 ··· 𝑦−𝑦 𝑛 𝑦1−𝑦0 𝑦1−𝑦2 ··· 𝑦1−𝑦 𝑛 𝑥1 + ⋯ + 𝑦−𝑦0 𝑦−𝑦1 ··· 𝑦−𝑦 𝑛−1 𝑦 𝑛−𝑦 𝑦 𝑛−𝑦1 ··· 𝑦 𝑛−𝑦 𝑛−1 𝑥 𝑛
  • 5. USE OF LAGRANGIAN INTERPOLATION  It is a process of computing intermediate values of a function from a given set of tabular values of the function.
  • 6. DIVIDED DIFFERENCE  Let 𝑦 = 𝑓(𝑥) be the given function which takes the values f(𝑥0), 𝑓(𝑥1) … 𝑓(𝑥 𝑛) corresponding to the arguments 𝑥0, 𝑥1, … 𝑥 𝑛 respectively, where the intervals 𝑥1 – 𝑥0 , 𝑥2 − 𝑥1 , … 𝑥 𝑛 – 𝑥 𝑛−1 need not equal
  • 7. REPRESENTATION BY DIVIDED DIFFERENCE TABLE 𝐴𝑟𝑔𝑢𝑚𝑒𝑛𝑡 𝑥 𝐸𝑛𝑡𝑟𝑦 𝑓(𝑥) 𝐹𝑖𝑟𝑠𝑡 𝐷. 𝐷 Δ1 𝑓(𝑥) 𝑆𝑒𝑐𝑜𝑛𝑑 𝐷. 𝐷 Δ1 2 𝑓(𝑥) 𝑇ℎ𝑖𝑟𝑑 𝐷. 𝐷 Δ1 3 𝑓(𝑥) 𝑥0 𝑥1 𝑥2 𝑥3 𝑥4 𝑓(𝑥0) 𝑓 𝑥1 𝑓 𝑥2 𝑓 𝑥3 𝑓(𝑥4) 𝑓 𝑥1 –𝑓 𝑥0 𝑥1 –𝑥0 = 𝑓 𝑥0, 𝑥1 𝑓 𝑥2 –𝑓 𝑥1 𝑥2 –𝑥1 = 𝑓 𝑥1, 𝑥2 𝑓 𝑥3 –𝑓 𝑥2 𝑥3 –𝑥2 = 𝑓 𝑥2, 𝑥3 𝑓 𝑥4 –𝑓 𝑥3 𝑥4 –𝑥3 = 𝑓 𝑥3, 𝑥4 𝑓 𝑥1,𝑥2 −𝑓 𝑥0,𝑥1 𝑥2−𝑥0 = 𝑓(𝑥0, 𝑥1, 𝑥2) 𝑓 𝑥2,𝑥3 −𝑓 𝑥1,𝑥2 𝑥3−𝑥1 = 𝑓(𝑥1, 𝑥2, 𝑥3) 𝑓 𝑥3,𝑥4 −𝑓 𝑥2,𝑥3 𝑥4−𝑥2 = 𝑓(𝑥2, 𝑥3, 𝑥4) 𝑓 𝑥1,𝑥2,𝑥3 −𝑓 𝑥0,𝑥1,𝑥2 x3−𝑥0 = 𝑓(𝑥0, 𝑥1, 𝑥2, 𝑥3) 𝑓 𝑥2,𝑥3,𝑥4 −𝑓 𝑥1,𝑥2,𝑥3 𝑥4−𝑥1 = 𝑓(𝑥1, 𝑥2, 𝑥3, 𝑥4)
  • 8. PROPERTIES OF DIVIDED DIFFERENCES  1. The divided differences are symmetrical in all their arguments, that is, the value of any difference is independent of the order of the arguments.  2. The divided difference of the product of a constant and a function is equal to the product of the constant and the divided difference of the function.  3. The operator Δ1 is linear  4. The 𝑛 𝑡ℎ divided difference of a polynomial of degree 𝑛 is a constant
  • 9. NEWTON DIVIDED DIFFERENCE INTERPOLATION  If 𝑓(𝑥) is a polynomial of degree𝑛, and 𝑓(𝑥0), 𝑓(𝑥1), … 𝑓(𝑥 𝑛) are the corresponding values of arguments 𝑥0, 𝑥1, … . 𝑥 𝑛 respectively, not necessarly equally spaced.  Then 𝑓 𝑥 = 𝑓 𝑥0 + ( 𝑥 −
  • 10. INTERPOLATION WITH EQUAL INTERVALS  FORWARD DIFFERENCE  If 𝑦0, 𝑦1, … 𝑦𝑛 are the values of 𝑦 = 𝑓(𝑥) corresponding to the arguments 𝑥0, 𝑥1, … 𝑥 𝑛 , where 𝑥1 − 𝑥0 , 𝑥2 − 𝑥1, … 𝑥 𝑛 − 𝑥 𝑛−1 are equal  𝑖. 𝑒 𝑥𝑖 = 𝑥0 + 𝑖ℎ, 𝑖 = 0,1,2 … 𝑛  Define Δ𝑦0 = 𝑦1 − 𝑦0 , Δ𝑦1 = 𝑦2 − 𝑦1 … . Δ𝑦 𝑛−1 = 𝑦𝑛 − 𝑦 𝑛−1  And Δ2 𝑦0 = Δ𝑦1 − Δ𝑦0 , Δ2 𝑦1 = Δ𝑦2 − Δ𝑦1 … . Δ2 𝑦 𝑛−1 = Δ𝑦𝑛 − Δ𝑦 𝑛−1  And so on  Here Δ is called Newton’s forward difference operator
  • 11.  NEWTON’S FORWARD DIFFERENCE FORMULA  If 𝑦0, 𝑦1, … 𝑦𝑛 are the values of 𝑦 = 𝑓(𝑥) corresponding to the arguments 𝑥0, 𝑥1, … 𝑥 𝑛  Then y = 𝑦0 + 𝑝∆𝑦0 + 𝑝 𝑝−1 2! ∆2 𝑦0 + 𝑝 𝑝−1 𝑝−2 3! ∆3 𝑦0 + ⋯  Where 𝑝 = 𝑥−𝑥0 ℎ .
  • 12. FORWARD DIFFERENCE TABLE 𝑥 𝑦 Δ Δ2 Δ3 Δ4 Δ5 𝑥0 𝑥1 𝑥2 𝑥3 𝑥4 𝑥5 𝑦0 𝑦1 𝑦2 𝑦3 𝑦4 𝑦5 Δ𝑦0 Δ𝑦1 Δ𝑦2 Δ𝑦3 Δ𝑦4 Δ2 𝑦0 Δ2 𝑦1 Δ2 𝑦2 Δ2 𝑦3 Δ3 𝑦0 Δ3 𝑦1 Δ3 𝑦2 Δ4 𝑦0 Δ4 𝑦1 Δ5 𝑦0
  • 13. BACKWARD DIFFERENCE  The differences 𝑦1 − 𝑦0, 𝑦2 − 𝑦1, … . 𝑦𝑛 − 𝑦 𝑛−1 are called first backward differences and denoted by  𝛻𝑦1 = 𝑦1 − 𝑦0, 𝛻𝑦2 = 𝑦2 − 𝑦1, … . 𝛻𝑦𝑛 = 𝑦𝑛 − 𝑦 𝑛−1  And 𝛻2 𝑦1 = 𝛻𝑦1 − 𝛻𝑦0, 𝛻2 𝑦2 = 𝛻𝑦2 − 𝛻𝑦1, … . 𝛻2 𝑦𝑛 = 𝛻𝑦𝑛 − 𝛻𝑦 𝑛−1 and so on
  • 14. NEWTON’S BACKWARD DIFFERENCE FORMULA  If 𝑦0, 𝑦1, … 𝑦𝑛 are the values of 𝑦 = 𝑓(𝑥) corresponding to the arguments 𝑥0, 𝑥1, … 𝑥 𝑛  Then 𝑦 = 𝑦𝑛 + 𝑝𝛻𝑦𝑛 + 𝑝 𝑝+1 2! 𝛻2 𝑦𝑛 + 𝑝 𝑝+1 𝑝+2 3! 𝛻3 𝑦𝑛 + ⋯  Where 𝑝 = 𝑥−𝑥 𝑛 ℎ .
  • 15. BACKWARD DIFFERENCE TABLE 𝑥 𝑦 𝛻 𝛻2 𝛻3 𝛻4 𝛻5 𝑥0 𝑥1 𝑥2 𝑥3 𝑥4 𝑥5 𝑦0 𝑦1 𝑦2 𝑦3 𝑦4 𝑦5 𝛻𝑦1 𝛻𝑦2 𝛻𝑦3 𝛻𝑦4 𝛻𝑦5 𝛻2 𝑦2 𝛻2 𝑦3 𝛻2 𝑦4 𝛻2 𝑦5 𝛻3 𝑦3 𝛻3 𝑦4 𝛻3 𝑦5 𝛻4 𝑦4 𝛻4 𝑦5 𝛻5 𝑦5
  • 17. DERIVATIVES USING DIVIDED DIFFERENCE  Procedure  Step 1. By using Newton’s divided difference formula find 𝑓(𝑥) in terms of x  Step 2. Find the derivatives of 𝑓(𝑥)
  • 18. DERIVATIVE - USING NEWTON’S FORWARD DIFFERENCE FORMULA  The first derivative of y at 𝑥 = 𝑥0 + 𝑝ℎ (near beginning of the data) is 𝑑𝑦 𝑑𝑥 = 𝑑𝑦 𝑑𝑝 𝑑𝑝 𝑑𝑥  𝑑𝑦 𝑑𝑥 = 1 ℎ ∆𝑦0 + 2𝑝−1 2! ∆2 𝑦0 + 3𝑝2−6𝑝+2 3! ∆3 𝑦0 + ⋯  The second derivative of y at 𝑥 = 𝑥0 + 𝑝ℎ is 𝑑2 𝑦 𝑑𝑥2 = 𝑑2 𝑦 𝑑𝑝2 𝑑𝑝 𝑑𝑥 2  𝑑2 𝑦 𝑑𝑥2 = 1 ℎ2 ∆2 𝑦0 + (𝑝 − 1)∆3 𝑦0 + 6𝑝2−18𝑝+11 12 ∆4 𝑦0 + ⋯  The third derivative y at 𝑥 = 𝑥0 + 𝑝ℎ  𝑑3 𝑦 𝑑𝑥3 = 1 ℎ3 ∆3 𝑦0 + 12𝑝−18 12 ∆4 𝑦0+. .  For tabular values, at 𝑥 = 𝑥0, (𝑝 = 0)  𝑑𝑦 𝑑𝑥 = 1 ℎ ∆𝑦0 − ∆2 𝑦0 2 + ∆3 𝑦0 3 − ∆4 𝑦0 4 + ⋯  𝑑2 𝑦 𝑑𝑥2 = 1 ℎ2 ∆2 𝑦0 − ∆3 𝑦0 + 11 12 ∆4 𝑦0 − ⋯  𝑑3 𝑦 𝑑𝑥3 = 1 ℎ3 ∆3 𝑦0 − 3 2 ∆4 𝑦0+. .
  • 19. DERIVATIVE - USING NEWTON’S BACKWARD DIFFERENCE FORMULA  The first derivative of y at 𝑥 = 𝑥 𝑛 + 𝑝ℎ (near end of the data) is 𝑑𝑦 𝑑𝑥 = 𝑑𝑦 𝑑𝑝 𝑑𝑝 𝑑𝑥  𝑑𝑦 𝑑𝑥 = 1 ℎ 𝛻𝑦 𝑛 + 2𝑝+1 2! 𝛻2 𝑦 𝑛 + 3𝑝2+6𝑝+2 3! 𝛻3 𝑦 𝑛 + ⋯  The second derivative of y at 𝑥 = 𝑥 𝑛 + 𝑝ℎ is 𝑑2 𝑦 𝑑𝑥2 = 𝑑2 𝑦 𝑑𝑝2 𝑑𝑝 𝑑𝑥 2  𝑑2 𝑦 𝑑𝑥2 = 1 ℎ2 𝛻2 𝑦 𝑛 + (𝑝 + 1)𝛻3 𝑦 𝑛 + 6𝑝2+18𝑝+11 12 𝛻4 𝑦0 + ⋯  The third derivative of y at 𝑥 = 𝑥 𝑛 + 𝑝ℎ  𝑑3 𝑦 𝑑𝑥3 = 1 ℎ3 𝛻3 𝑦 𝑛 + 12𝑝+18 12 𝛻4 𝑦0+. .  For tabular values, at 𝑥 = 𝑥 𝑛, (𝑝 = 0)  𝑑𝑦 𝑑𝑥 = 1 ℎ 𝛻𝑦 𝑛 + 𝛻2 𝑦 𝑛 2 + 𝛻3 𝑦 𝑛 3 + ⋯  𝑑2 𝑦 𝑑𝑥2 = 1 ℎ2 𝛻2 𝑦 𝑛 + 𝛻3 𝑦 𝑛 + 11 12 𝛻4 𝑦0 + ⋯  𝑑3 𝑦 𝑑𝑥3 = 1 ℎ3 𝛻3 𝑦 𝑛 + 3 2 𝛻4 𝑦0+. .
  • 20. NUMERICAL INTEGRATION SINGLE (LINEAR) INTEGRATION 1. TRAPEZOIDAL RULE 2. SIMPSON’S 𝟏 𝟑 RULE
  • 21. TRAPEZOIDAL RULE  𝑥0 𝑥1 𝑓(𝑥) 𝑑𝑥 = ℎ 2 𝑦0 + 𝑦𝑛 + 2( 𝑦1 + 𝑦2 +
  • 22. SIMPSON’S 𝟏 𝟑 𝒓𝒅 RULE  𝑥0 𝑥1 𝑓(𝑥) 𝑑𝑥 = ℎ 3 𝑦0 + 𝑦𝑛 + 4 𝑦1 + 𝑦3 + 𝑦5 + ⋯ + 2(𝑦2 + 𝑦4 + 𝑦6+. . ) = ℎ 3 𝑓𝑖𝑟𝑠𝑡 + 𝑙𝑎𝑠𝑡 + 4 𝑠𝑢𝑚 𝑜𝑓 𝑜𝑑𝑑 𝑡𝑒𝑟𝑚𝑠 + 2 𝑠𝑢𝑚 𝑜𝑓 𝑒𝑣𝑒𝑛 𝑡𝑒𝑟𝑚𝑠 ]  ℎ = 𝑥1−𝑥0 𝑛 , 𝑛 − 𝑖𝑠 𝑡ℎ𝑒 𝒆𝒗𝒆𝒏 𝑛𝑜 𝑜𝑓 𝑠𝑢𝑏 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙𝑠 𝑖𝑛 𝑥0 𝑥1  Condition for applying the Simpson’s rule – Number of subintervals must be even
  • 23. NUMERICAL DOUBLE INTEGRATION  1. 𝐓𝐑𝐀𝐏𝐄𝐙𝐎𝐈𝐃𝐀𝐋 𝐑𝐔𝐋𝐄  2. 𝐒𝐈𝐌𝐏𝐒𝐎𝐍’𝐒 𝐑𝐔𝐋𝐄
  • 24. TRAPEZOIDAL RULE  𝑎 𝑏 𝑐 𝑑 𝑓 𝑥, 𝑦 𝑑𝑥𝑑𝑦 = ℎ𝑘 4 𝑓1 + 𝑓3 + 𝑓7 + 𝑓9 + 2 𝑓2 + 𝑓4 + 𝑓6 + 𝑓8 + 4𝑓5]  = ℎ𝑘 4 𝑆𝑢𝑚 𝑜𝑓 𝑐𝑜𝑟𝑛𝑒𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 + 2 𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑜𝑢𝑛𝑑𝑎𝑟𝑦 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 + 4(𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑖𝑛𝑡𝑒𝑟𝑖𝑜𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓(𝑥, 𝑦)]
  • 25. y x 𝑥0 𝑥1 𝑥2 𝑥3 𝑦0 𝑓(𝑥0, 𝑦0) 𝑓(𝑥1, 𝑦0) 𝑓(𝑥2, 𝑦0) 𝑓(𝑥3, 𝑦0) 𝑦1 𝑓(𝑥0, 𝑦1) 𝑓(𝑥1, 𝑦1) 𝑓(𝑥2, 𝑦1) 𝑓(𝑥3, 𝑦1) 𝑦2 𝑓(𝑥0, 𝑦2) 𝑓(𝑥1, 𝑦2) 𝑓(𝑥2, 𝑦2) 𝑓(𝑥3, 𝑦2) 𝑦3 𝑓(𝑥0, 𝑦3) 𝑓(𝑥1, 𝑦3) 𝑓(𝑥2, 𝑦3) 𝑓(𝑥3, 𝑦3) For example, if x takes the values 𝑥0, 𝑥1, 𝑥2, 𝑥3 and y takes values 𝑦0, 𝑦1, 𝑦2, 𝑦3 Red indicates – corner values Blue indicates – boundary values Black indicates – interior values
  • 26. 𝑺𝑰𝑴𝑷𝑺𝑶𝑵’𝑺 𝑹𝑼𝑳𝑬  𝑎 𝑏 𝑐 𝑑 𝑓 𝑥, 𝑦 𝑑𝑥𝑑𝑦 = ℎ𝑘 9 𝑓1 + 𝑓3 + 𝑓7 + 𝑓9 + 2 𝑓2 + 𝑓4 + 𝑓6 + 𝑓8 + 16𝑓5]  = ℎ𝑘 9 𝑆𝑢𝑚 𝑜𝑓 𝑐𝑜𝑟𝑛𝑒𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 + 4 𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑏𝑜𝑢𝑛𝑑𝑎𝑟𝑦 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓 𝑥, 𝑦 + 16(𝑆𝑢𝑚 𝑜𝑓 𝑡ℎ𝑒 𝑖𝑛𝑡𝑒𝑟𝑖𝑜𝑟 𝑣𝑎𝑙𝑢𝑒𝑠 𝑜𝑓 𝑓(𝑥, 𝑦)]
  • 27. Errors in Trapezoidal rule of numerical integration.  When evaluating 𝑎 𝑏 𝑓 𝑥 𝑑𝑥, the error in the trapezoidal rule is  < 𝑏−𝑎 2 12 ℎ2 𝑀, where ℎ = 𝑏−𝑎 𝑛 , n is the number of subintervals of (a, b),  And 𝑀 = 𝑚𝑎𝑥{|𝑦0 ′′ |, |𝑦1 ′′ |,· · · , |𝑦 𝑛−1 ′′ |}, 𝑦𝑟′′ = 𝑓′′(𝑥 𝑟)  Error in Trapezoidal rule is of order 𝒉 𝟐
  • 28. Errors in Simpson’s rule of numerical integration  The error in Simpson’s rule is < 𝑏−𝑎 180 ℎ4 𝑀  where ℎ = 𝑏−𝑎 2𝑛 , 2n is the number of subintervals of (a, b),  𝑀 = 𝑚𝑎𝑥 𝑦0 1 , 𝑦1 4 ,· · ·