Math 262 Equation Sheet

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Math 262 Equation Sheet INFINITE SEQUENCES

ak .

f (x) =

Review Let

{a n } be a sequence. If nlim an → +∞

=L

lim a n

[

then

forms:

use

Divergence Test

lim a n = L

n → +∞

Name

Root Test

lim c = c

lim ca n = c lim a n = cL

n → +∞

n→+∞

n→+∞

n→+∞

n→+∞

n→+∞

n→+∞

n→+∞

n→+∞

lim a n

n→+∞

a lim n = n→+∞ = n → +∞ bn lim bn M

M ≠0 Squeeze Theorem For Sequences

Let that

{a n }, {bn }, and {cn } be sequences such {a n } ≤ {cn } ≤ {bn } . If lim a n = L

and



1

∑1 bk ∞

a k ≤ bk for all k . converges, then





1





1

ak

ak

arctan x = x −

ex = 1+



1

ak

and

Name Alternating Series Test

x3 x5 x7 + − +. 3 5 7

x x2 x3 x 4 + + + + ... 1! 2! 3! 4!

cos x = 1 −

diverges.



x2 x3 x4 + − + .... 2 3 4

x3 x5 x7 x9 + − + .... sin x = x − 3! 5! 7! 9!

diverges, then also

Suppose that

= 1 + 2 x + 3 x 2 + 4 x 3 + .....

bk





1

−1 ≤ x ≤ 1



= ∑ xn ∞

= ∑ nx n −1

−1 ≤ x ≤ 1

x 2 x 4 x6 x8 + − + − .... 2! 4! 6! 8!

n



= ∑ (− 1) 1

n



= ∑ (− 1) 1



=∑ 1





(2n + 1)! n

−1 ≤ x ≤ 1

−1 ≤ x ≤ 1

(− ∞, ∞ )

x 2 n +1

n

= ∑ (− 1) 1

x 2 n +1 2n + 1

xn n!

= ∑ (− 1) 1

xn n

x 2n (2n)!

(− ∞, ∞ ) (− ∞, ∞ )

bk

are two series with positive terms with

ak bk If p > 0 ⇒ either both series

n → +∞

TESTS TO DETERMINE THE CONVERGENCE/DIVERGENCE OF A SERIES

ak



VECTORS AND COORDINATE GEOMETRY

k → +∞

lim bn = L ⇒ lim c n = L

n → +∞



Radius of Convergence

1

p = lim

n → +∞

and



(1 − x )2

ln ( x + 1) = x −

are two series with positive terms

∑1 bk Limit Comparison Test

n → +∞

p = 1 ⇒ no conclusion.



L provided that

Sigma Notation

1 = 1 + x + x 2 + x 3 + x 4 . + ... 1− x

1

1

If

Form

1

converges.

lim(anbn ) = liman • limbn = LM

Quotient

POWER OF SERIES AND RADIUS OF CONVERGENCE

p = lim k a k

Suppose that

If

lim(an − bn ) = lim an − lim bn = L − M

Product

ak +1 ak

is a series of positive terms

such that

n → +∞

lim(an +bn ) = liman + limbn = L+M

Difference

k

a k +1 ak

is a series of positive terms

k

If p > 1 ⇒ the series diverges. If p < 1 ⇒ the series converges.

Comparison Test

p = lim

If p > 1 ⇒ the series diverges.

k → +∞

p = lim

∑a

If

is a series of nonzero terms

If p < 1 ⇒ the series converges. If p = 1 ⇒ no conclusion.

k → +∞

n → +∞

Constant Multiple Additive

=±∞

lim a k ≠ 0

diverges if

k

p = 1 ⇒ no conclusion.

with

and

Property

Constant

k

k → +∞

k → +∞

a

∑a

If

then the following results are true

n → +∞

Convergence

If p > 1 ⇒ the series diverges. If p < 1 ⇒ the series converges.

Properties of Sequences

lim bn = M

∫ f ( x)dx

k →+∞

f ( x) f ' ( x) = lim lim x→a g ( x) x →a g ' ( x)

sequences with

∑a with

{a n } and {bn } be two convergent

∑a

Ratio Test Absolute

with +∞

lim a k = 0

decreasing, and 2.

a

Ratio Test

L’Hoptial’s Rule

is defined. The series

f ( x)dx

diverges if

L’Hopital’s Rule to evaluate the limit.

Suppose that

)

+∞



0 ∞ 0 0 ∞ , ,0 , ∞ ,1 , ∞ − ∞ 0 ∞

The series converges if and only if 1. a k +1 ≤ a k ; the series is

if

results in either one of the following

n → +∞

If the function is

decreasing and continuous on a,+∞ , then the series converges

the sequence converges. If

− a1 + a 2 − a3 + a 4 − ....

and

converge, or both series diverge. What Does It Say Suppose that

ak > 0

for

k = 1,2,3,... then the series has the

Vectors & Vector Dot Products Let

u

be a vector having n components, then the

length or norm of is

u defined to be

form of either: Name Integral Test

∑a

k

What Does It Say is a series of positive terms

a1 − a 2 + a3 − a 4 +…. or

u =

(n1 )2 + (n2 )2 + (n3 )2 + ... + (n n )2

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u

t

2.

s = s(t ) = ∫ r ' (t ) dt

v

Let and be two vectors, then their dot product is defined to be:

lim

( x , y ) → ( a ,b )

f ( x , y ) = f ( a , b)

t0

Partial Derivatives

u ⋅ v = u v cos θ

Formulas for Curvature, Torsion, Radius of Curvature

Properties

Name

Symmetry

u ⋅v = v⋅u k

Linearity

Suppose that u is a vector having n components, then its unit vector is found be dividing each component of the vector by its norm. That is,

1

u=

u

(n1 )

Similarly the partial with respect to y, at the point (a, b ) , denoted as f , is defined to be

1

y

κ v×a v×a

f y = lim k →0

(v × a ) da

f ( a , b + k ) − f (b ) k

In practice we use the following

f x = f1 =

∂f ∂x



f y = f2 =

∂f ∂y



dv 2 T + v κN dt dt

v×a

h

2

differentiate the function f with respect to x while holding all other variables as constants. differentiate the function f with respect to y while holding all other variables as constants.

Frenet – Serret Formulas

+ (n2 ) + (n3 ) + ... + (n n ) 2

a=

τ=

1 2

3

dT N = B × T = dt dT dt

Tangential and Normal Components Torsion

Unit Vectors

=

B=

h→0

v×a

ρ=

Unit Normal Vector

⎛u ⋅v⎞ ⎟ θ = cos −1 ⎜⎜ ⎟ u v ⎝ ⎠

unit

κ=

Binormal Vector



f x (a, b) = lim

v

Radius of Curvature

A. Show orthoganality: u ⋅ v = 0 u⊥v B. Finding the angle between two vectors:

www.prep101.com f ( a + h, b ) − f ( a )

v

v

Uses of Dot Product

u

T=

Curvature

R

x , denoted as f x , at the point (a, b) is defined to be

Formula

Unit Tangent Vector

(k u )⋅ v = k (u ⋅ v) ∈ u (v + w) = u ⋅ v + u ⋅ w

Multiplication with a scalar

Given a function f ( x, y ) , the partial with respect to

2

2

u

dT = κN ds

dB = −τ N ds

dN = −κ T + τ B ds

The idea can easily be extended to functions having more than 2 variables. Higher Derivatives

VECTOR VALUED FUNCTIONS Tangent Directions If

to the points on the curve

is a position vector

(x(t ), y(t ), z(t )) then

we can find the following quantities

v avg =

r (t + ∆t ) − r (t ) ∆t = , ∆t

change in time Velocity

v (t ) = r ' (t ) =

dr dx dy [ y(t )] j + dz [z (t )]k = [x(t )]i + dt dt dt dt

lim

( x , y ) →( a ,b )

f ( x, y ) = L

Implies that A. Every neighborhood of (a, b) contains points of the domain of f ( x, y ) different from (a, b). B.

For every ε (positive) there exists a positive δ such that f ( x, y ) − L < ε whenever (x, y) is in the domain of inequality:

Speed

0
0

⇒ w e h a v e a lo c a l m in im u m

If d e t(D )< 0

and

a+c< 0

⇒ w e h a v e a lo c a l m a x im u m

Lagrange Multipliers To find the extreme values: 1. 2.

First get it into a Lagrangian function: L ( x, y ) = f ( x, y ) + λ g ( x, y ) Solve for the critical point by finding out when

0= 3.

u$

direction

∂ ∂ ∇f ( x, y ) = $i ( x, y ) + $j ( x, y ) ∂x ∂y

The chain rule can be extended to include functions which have more than one variable.

= Directional derivative of f with

∂L ∂L ∂L = f x ( x, y ) + λ g ( x , y ) , 0 = g ( x, y ) = f y ( x , y ) + λ g ( x, y ) , 0 = ∂x ∂λ ∂y

Once the critical points have been found, plug it back into the function and test to see which point satisfies the given criteria.

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