L’Hospital’s Rule: f and g – differentiable, g(a) 0 near a (except possibly at a). If...

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L’Hospital’s Rule: f and g – differentiable, g(a) 0 near a (except possibly at a). If (indeterminate form of type ) or (indeterminate form of type ) then (if this limit exists). 0 ) ( lim 0 ) ( lim x g and x f a x a x ) ( lim ) ( lim x g and x f a x a x 0 0 ) ( ) ( lim ) ( ) ( lim x g x f x g x f a x a x ? ) ( ) ( lim x g x f a x

Transcript of L’Hospital’s Rule: f and g – differentiable, g(a) 0 near a (except possibly at a). If...

Page 1: L’Hospital’s Rule: f and g – differentiable, g(a)  0 near a (except possibly at a). If (indeterminate form of type ) or (indeterminate form of type )

L’Hospital’s Rule:

f and g – differentiable, g(a) 0 near a (except possibly at a).

If (indeterminate form of type )

or (indeterminate form of type )

then (if this limit exists).

0)(lim0)(lim

xgandxfaxax

)(lim)(lim xgandxfaxax

0

0

)(

)(lim

)(

)(lim

xg

xf

xg

xfaxax

?)(

)(lim xg

xfax

Page 2: L’Hospital’s Rule: f and g – differentiable, g(a)  0 near a (except possibly at a). If (indeterminate form of type ) or (indeterminate form of type )

Indeterminate Product

If (indeterminate form of type )

then use L’Hospital Rule for

)(lim0)(lim xgandxfaxax

0

.)(1

)(lim

)(1

)(lim

xf

xgor

xg

xfaxax

Indeterminate Difference

If (indeterminate form of type )

then try to convert into quotent and use L’Hospital Rule.

)(lim)(lim xgandxfaxax

?)()(lim

xgxfax

?)()(lim

xgxfax

Indeterminate Power

If (indeterminate form of type )

or (indeterminate form of type )

or (indeterminate form of type )

then use

0)(lim0)(lim

xgandxfaxax

00

?)(lim )(

xg

axxf

0)(lim)(lim

xgandxfaxax

)(lim1)(lim xgandxfaxax

0

1

).(ln)()(ln)( )()(ln)()( xfxgxforexf xgxfxgxg

Page 3: L’Hospital’s Rule: f and g – differentiable, g(a)  0 near a (except possibly at a). If (indeterminate form of type ) or (indeterminate form of type )

Improper Integrals

Type I:

Infinite IntervalType II:

Discontinuous Integrand

.)()()(

)()().

;)(lim)()().

;)(lim)()().

a

a

a

a

b

tt

bb

t

t

at

a

t

a

dxxfdxxfdxxf

convergentdxxfanddxxfaIfc

dxxfdxxfbtexistsdxxfIfb

dxxfdxxfatexistsdxxfIfa

Type I Improper Integral:

If limit exists then this integral is con

vergent,

otherwise – divergen

t.

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Type II Improper Integral:

a). If f – continuous on [a,b) and discontinuous at b

b). If f – continuous on (a,b] and discontinuous at a

c). If f – discontinuous at c(a,b) and

;)(lim)(

t

abt

b

a

dxxfdxxf

;)(lim)(

b

tat

b

a

dxxfdxxf

.)()()(

)()(

b

c

c

a

b

a

b

c

c

a

dxxfdxxfdxxf

convergentdxxfanddxxf

If limit exists then this integral is con

vergent,

otherwise – divergen

t.

Comparison Th for Improper Integrals:f and g – continuous, f(x)g(x) 0 for xa.

.)()().

;)()().

divergentdxxfdivergentdxxgIfb

convergentdxxgconvergentdxxfIfa

aa

aa

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Differential equation –

Equation that contains an unknown function and some of its derivatives.

Order of differential equation = order of highest derivative in equations.

f(x) – solution of differential equation, if it satisfies the equation for all x in some interval.

Solve differential equation = find ALL possible solutions.

Condition of the form y(t0)=y0 – initial condition.

Initial-value Problem (IVP) – find solution that satisfies the given initial condition.

Separable equation –

1st order differential equation in which expression for dy/dx can be factored as a function of x times a function of y:

)()( yfxgdx

dy

Page 6: L’Hospital’s Rule: f and g – differentiable, g(a)  0 near a (except possibly at a). If (indeterminate form of type ) or (indeterminate form of type )

dxxgdyyh

yfifyf

yhdxxgdyyhyfxgdx

dy

)()(

0)()(

1)()()()()(

Mixing problem:

A tank contains 20 kg of salt dissolved in 5000L of water. Brine that contains 0.03 kg of saltper liter of water enters the tank at a rate of 25L/min. The solution is kept throughly mixedand drains from the tank at the same rate. How much salt remains in the tank after half an hour?