Cheatography

# Calculus II Cheat Sheet by CROSSANT

Master cheat sheet for Calculus II.

### Series

 Series Type General Summation Conver­gence Divergence Notes Infinite Series Σan=Σ∞n=k an Converges if lim n->∞ Sn=L Diverges if lim n->∞ =∞ or DNE Sn is the partial sum of the series: Sn=a1+a2+a3+a4+...+an-1+an Harmonic Series Σ1/n Never converges Always diverges The altern­ating version of this series (Σ(-1)n+1/n) converges, and Σ1/n is a P-Series with p=1 Geometric Series Σ∞n=0 arn=Σ∞n=1 arn-1 Converges if |r|<1 Diverges if |r|≥1 If the series converges, its sum is S=a/(1-r) P-Series Σ1/np Converges if p>1 Diverges if p≤1 Altern­ating Series Σ(-1)nbn, Σ(-1)n+1bn, or Σ(-1)n-1bn Converges if lim n->∞ =0 and bn is a decreasing sequence (bn+1≤bn for all n) Cannot show diverg­ence, inconc­lusive Telesc­oping Series Σ(bn-bn+1) Converges if lim n->∞ =L Diverges if lim n->∞ Sn=∞ or DNE Sn is the partial sum of the series: Sn=Σni=1(bi-bi+n) where n is finite
Altern­ating Series Estimation Theorem: If Snni=1(-1)nbn or Σni=1(-1)n-1bn is the sum of an altern­ating series that converges, then |Rn|=|S-Sn|≤bn+1
Trigon­ometric functions like cos(nπ) or sin(nπ­+π/2) act as sign altern­ators, like (-1)n
The Altern­ating Series Test does not show diverg­ence, however, implem­enting the test requires a Test For Diverg­ence, which does show divergence

### Series Tests

 Test Type Typical series to use test Conver­gence Divergence Notes Test for Divergence Σan Cannot show conver­gence, inconc­lusive Diverges if lim n->∞ ≠0 Integral Test Σan=f(n), which is a positive, contin­uous, decreasing function on the interval [k,∞), usually with easily­-in­teg­rable functions Converges if ∫k∞ f(n)dn converges Diverges if ∫k∞ f(n)dn diverges (Direct) Comparison Test an and bn are positi­ve-­termed (an≥0 and bn≥0 for all n) and an≤bn for all n Σan converges if Σbn converges Σbn diverges if Σan diverges Inconc­lusive if bn diverges or an converges Limit Comparison Test an and bn are positi­ve-­termed, and lim n->∞ an/bn=c, or lim n->∞ bn/an=d, where c and d are finite constants greater than 0 Σan converges ⟺ Σbn converges Σan diverges ⟺ Σbn diverges Inconc­lusive if either c or d=0 or ∞ Ratio Test Σan, usually with n! terms or ann Absolutely converges if lim n->∞ |an+1/an|<1 Diverges if lim n->∞ |an+1/an|>1 Inconc­lusive if lim n->∞ |an+1/an|=1 Root Test Σan, usually with ann Absolutely converges if lim n->∞ |an|1/n<1 Diverges if lim n->∞ |an|1/n>1 Inconc­lusive if lim n->∞ |an|1/n=1 Absolu­te/­Con­dit­ional Conver­gence Σan Absolutely converges if Σ|an| converges Condit­ionally converges if Σ|an| diverges, but Σan converges Diverges if Σan diverges
For the series listed, assume each series to be an infinite series starting at n=k: Σn=k
If Test for Divergence passes (lim n->∞ =0), use another test
The symbol [ ⟺ ] represents the relati­onship "if and only if" (often abbrev­iated to "­iff­"), meaning both sides of the statement must be true at the same time, or false at the same time
If a test is inconc­lusive, use another test

### Special Series

 Series Summation Form First five terms Radius and Interval of Conver­gence Power Series centered at a ΣCn(x-a)n C0+C1(x-a)+C2(x-a)2+C3(x-a)3+C4(x-a)4+... Taylor Series centered at a Σf(n)(a)(x-a)n/n! f(a)+f­'(a­)(x­-a)­+f'­'(a­)(x-a)2/2!+f'­''(­a)(x-a)3/3!+f(4)(a)(x-a)4/4!+... R>|x-a| Maclaurin Series (Taylor Series centered at 0) Σf(n)(0)(x-0)n/n!=Σf(n)(0)xn/n! f(0)+f­'(0­)x+­f''(0)x2/2!+f'­''(0)x3/3!+f(4)(0)x4/4!+... 1/(1-x) Σxn 1+x+x2+x3+x4+... R=1, I=(-1,1) ex Σxn/n! 1+x+x2/2!+x3/3!+x4/4!+... R=∞, I=(-∞,∞) ln(1+x) Σ(-1)n+1xn/n x-x2/2+x3/3-x4/4+x5/5+... R=1, I=(-1,1] arctan(x) Σ(-1)nx2n+1/(2n+1) x-x3/3+x5/5-x7/7+x9/9+... R=1, I=[-1,1] sin(x) Σ(-1)nx2n+1/(2n+1)! x-x3/3!+x5/5!-x7/7!+x9/9!+... R=∞, I=(-∞,∞) cos(x) Σ(-1)nx2n/(2n)! 1-x2/2!+x4/4!-x6/6!+x8/8!+... R=∞, I=(-∞,∞) (1+x)k Σ(kn)xn=Σ((k(­k-1­)(k­-2)­(k-­3)...(­k-n­+1)­)/n!)xn 1+kx+k­(k-1)x2/2!+k(­k-1­)(k-2)x3/3!+k(­k-1­)(k­-2)­(k-3)x4/4!+... R=1 Taylor's Inequality |Rn(x)|≤M­|x-a|n+1/(n+1)!, given M≥|f(n+1)(x)| for all |x-a|≤d
For the series listed, assume each series to be an infinite series starting at n=0: Σn=0
Note that the formula for a Degree 1 Taylor Polyno­mial, T1(x), has the same formula as the Linear Approx­imation formula learned in Calculus I
f(n) means "the nth derivative of the function f"
n!=n(n­-1)­!=n­(n-­1)(­n-2­)!=­n(n­-1)­(n-­2)(­n-3­)!=...
n! = n(n-1)­(n-­2)(­n-3­)...*3*2*1
0!=1, 1!=1

### Areas of Functions

 Between two functions ∫ab ((top functi­on)­-(b­ottom functi­on))dA Enclosed by a polar function ½∫ab f(θ)2dθ Between two polar functions ½∫ab ((outer polar function)2-(inner polar function)2)dθ
Area enclosed by a polar function is with respect to the pole, which is the origin

Average value of a function: favg=1/(b-a)∫ab f(x)dx

### Volumes of Solids of Revolution

For Cylind­rical Shells: radius=x or y, and height­=f(x) or g(y)

### Arc Lengths

 Function ∫ab √(1+(f'(x))2)dx Parametric Function ∫ab √((x'(t))2+(y'(t))2)dt Polar Function ∫ab √(r(θ)2+(r'(θ))2)dθ
For standard functions: f'(x)=­dy/dx
For parametric functions: x'(t)=­dx/dt and y'(t)=­dy/dt
For polar functions: r'(θ)=­dr/dθ

### Surface Areas

 Function revolved about an axis 2π∫ab (radiu­s)(Arc Length compon­ent)ds Function revolved about y-axis 2π∫ab x√(1­+(f­'(x))2)dx Function revolved about x-axis 2π∫ab y√(1+(g'(y))2)dy Parametric function of t revolved about y-axis 2π∫ab f(x)√((x'(t))2+(y'(t))2)dt Parametric function of t revolved about x-axis 2π∫ab g(y)√((x'(t))2­+(y'(t))2)dt
f'(x)=­dy/dx, g'(y)=­dx/dy, x'(t)=­dx/dt, and y'(t)=­dy/dt

### Integr­ation by Parts

 Indefinite Integral ∫udv=u­v-∫vdu Definite Integral ∫ab udv=uv|ab -∫ab vdu
Integr­ation by Parts is used to integrate integrals that have components multiplied together in their simplest form, often referred to as a "­product rule for integr­als­"

Choosing the "­dv" term depends on what will simplify the integral the best, while being relatively simple to integrate

The constant of integr­ation does not need to be inserted until the integral has been fully simplified

### Integr­ation by Partial Fractions

 (px+q)­/((­x-a­)(x-b)) A/(x-a) + B/(x-b) (px+q)­/(x-a)2 A/(x-a) + B/(x-a)2 (px²+q­x+r­)/(­(x-­a)(­x-b­)(x-c)) A/(x-a) + B/(x-b) + C/(x-c) (px2+qx+r)­/((x-a)2(x-b)) A/(x-a) + B/(x-a)2 + C/(x-b) (px2+qx+r)­/((­x-a)(x2+bx+c)) A/(x-a) + Bx+C/(x2+bx+c) ∫1/(a2+x2) dx (1/a)a­rct­an(­x/a)+C
Integr­ation by Partial Fractions is used to simplify integrals of polynomial rational expres­sions into simpler fractions with a factored, irredu­cible denomi­nator

The degree (highest power) of the numera­tor's polynomial must be less than the degree of the denomi­nator's polyno­mial, otherwise, polynomial long division must be used before converting the expression into partial fractions

### Improper Integrals

 ∫∞a f(x)dx lim t->∞ ∫at f(x)dx ∫b-∞ f(x)dx lim t->-∞ ∫tb f(x)dx ∫∞-∞ f(x)dx lim t->-∞ ∫tc f(x)dx + lim t->∞ ∫xt f(x)dx Conver­gence of ∫f(x)dx lim t->±∞ =L Divergence of ∫f(x)dx lim t->±∞ =±∞ or DNE
Improper Integrals are integrals with bounds at infinity (Type 1) or discon­tinuous bounds (Type 2)

### Parametric Curves and Polar Functions

 Parametric Curve C as a function of Parameter t (x,y)=­(f(­t),­g(t)) for t on [a,b] Slope at a given point dy/dx=­(dy­/dt­)/(­dx/dt) Second derivative d2y/dx2=(dy/d­t)/­(dx/dt)2 Polar Curve C as a function of Parameter θ (r,θ)=­(r,­θ±2­πn)­=(-­r,θ±πn) Slope at a given point dy/dx=­(dy­/dθ­)/(­dx/dθ) Cartes­ian­/Re­cta­ngular to Polar coordi­nates x=rcos(θ), y=rsin(θ) Polar to Cartes­ian­/Re­cta­ngular coordi­nates r2=x2+y2 or r=√(x2+y2), tanθ=y/x or θ=arct­an(y/x)
(dx/dt)≠0, (dx/dθ)≠0

### Integral Approx­ima­tions and Error Bounds

 Midpoint Rule Δx(f(x̄1)+f(x̄2)+f(x̄3)+...+f(x̄n-1)+f(x̄n)) Trapez­oidal Rule (Δx/2)(f(x1)+2f(x2)+2f(x3)+...+2f(xn-1)+f(x1)) Simpson's Rule (Δx/3)(f(x1)+4f(x2)+2f(x3)+4f(x4)+2f(x5))+...+­2f(xn-2)+4f(xn-1)+f(xn)) Midpoint Rule Error Bound |Em|≤k(b-a)3/24n2, k=f''(x)max on [a,b] Trapez­oidal Rule Error Bound |Et|≤k(b-a)3/12n2, k=f''(x)max on [a,b] Simpson's Rule Error Bound |Es|≤k(b-a)5/180n4, k=f(4)(x)max on [a,b]
Integral Approx­ima­tions are typically used to evaluate an integral that is very difficult or impossible to integrate

Δx=(b-a)/n

x̄=(xi-1+xi)/2, the averag­e/m­edian of two points xi-1 and xi

Simpson's Rule can only be used if the given n is even, that is, n=2k for some integer k.

In order of most accurate to least accurate approx­ima­tion: Simpson's Rule, Midpoint Rule, Trapez­oidal Rule, Left/Right endpoint approx­imation

Hey everyone! I noticed some errors in the Series Tests, apparently from a wrongful copy-and-paste that slipped by. If you downloaded this sheet before this comment was posted, please re-download it now that the errors are corrected. Thanks and happy studying! - CROSSANT

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