janhardo

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These are questions asked by janhardo

Contour integration notation

" (∫)[+infinity]^(+infinity)((-x)^(z))/((e)^(x)-1). (ⅆx)/(x)"

 

The limits of integration are intented to indicate a path of integration which begins at + ∞, moves to th e left down the positive real axis, circles the orign once in positive ( counterclockwise) direction, and returns up to the positive real axis to  +∞

-How does this contour look like  in a  graph ?
- the "(ⅆx)/(x)" notation  ?
- calculating this complexe contour integral?

Seems that the concept of the contour integration is similar wit a line integral in real calculus ?

NULL

Download contourintegraal_vraag1.mw

I following a example of products multiplication like this one

u:=n->Product(2*k-1,k=1..n)/Product(3*k-1,k=1..n)*x^n;

Calculating with  this with maple 1d input is correct, but when i convert a maple 1d input  to 2D input ( i did somewhere) and use this then there is difference with the maple 1d calculation

Seems to be not a advisable to use converted maple 1d to 2 D input for calculation : ( for a mixed calculation(maple input/2D input)  or solely 2d input) , but only for purpose of seeing what the expression in maple input is standing for.   

Note: i did the calculation again with mixed input and now the correct sequenze of answers shows up ?

The prime notation as used default on my keyboard is not the same as used in Maple.

NULL

restart;

with(student):

interface(typesetting = extended);

extended

(1)

Typesetting:-Settings(typesetprime = true);

true

(2)

diff(y(x), x)

diff(y(x), x)

(3)

y*`\`   `and  diff(y(x), x)are not working on my keyboard as prime?

 prime symbols (not showed)  not as (3)

 ========================================

restart

kernelopts(version)

`Maple 2021.1, X86 64 LINUX, May 19 2021, Build ID 1539851`

(4)

interface(typesetting = extended)

diff(y(x), x)

diff(y(x), x)

(5)

Typesetting:-Settings(typesetprime = true)

diff(y(x), x)

diff(y(x), x)

(6)

"y^((3))"

diff(diff(diff(y(x), x), x), x)

(7)

PDEtools:-declare(y(x))

y(x)*`will now be displayed as`*y

(8)

diff(y(x), x)

diff(y(x), x)

(9)

"y^((3))"

diff(diff(diff(y(x), x), x), x)

(10)

PDEtools:-declare(f(x, y))

f(x, y)*`will now be displayed as`*f

(11)

diff(f(x, y), y, x, y)

diff(diff(diff(f(x, y), x), y), y)

(12)

=================================================

Application Differential equation :  

int((10000*k/(100*k*P(t) - 1) - 100/P(t))*diff(P(t), t), t = 0 .. t) = t;

int((10000*k/(100*k*P(t)-1)-100/P(t))*(diff(P(t), t)), t = 0 .. t) = t

(13)

P(t)=solve(%,P(t));

Error, (in solve) cannot solve expressions with diff(P(t), t) for P(t)

 

This error .. see  Applications to Differential Equations

Applications to Differential Equations

   

 

NULL

Download vraag_over_dv_in_harald_pleym_-error_.mw

Also a error in old studymaterial : how to be fixed ? ...or obselote now this calculation and must be replaced for a modern calculation in Maple ?

Thought always that the round d is reserved for function of two variables x,y , but  that seems to be not the case here ?

restart;

Comparing Different Answers

 

Een antwoord ergens gegeven is

Int(sqrt(x^2+1), x) = (1/2)*x*sqrt(x^2+1)+(1/2)*ln(x+sqrt(x^2+1)) + C                                                             (vb)

 

Mple geeft

 

Int(sqrt(x^2+1),x)=int(sqrt(x^2+1),x)+C[1];

Int((x^2+1)^(1/2), x) = (1/2)*x*(x^2+1)^(1/2)+(1/2)*arcsinh(x)+C[1]

(1)

 

De twee antwoorden lijken nog niet opelkaar !
In het gegeven antwoord staat er een ln en in Maple kan een expressie omgezet worden in ln termen
  

convert(%,ln);

Int((x^2+1)^(1/2), x) = (1/2)*x*(x^2+1)^(1/2)+(1/2)*ln(x+(x^2+1)^(1/2))+C[1]

(2)

(2)  is hetzelfde (vb)

Dezelfde integraal i sook gegeven als

Int(sqrt(x^2+1),x)=((x+sqrt(x^2+1))^2+4*ln(x+sqrt(x^2+1))-(x+sqrt(x^2+1))^(-2))/8+C[2];

Int((x^2+1)^(1/2), x) = (1/8)*(x+(x^2+1)^(1/2))^2+(1/2)*ln(x+(x^2+1)^(1/2))-(1/8)/(x+(x^2+1)^(1/2))^2+C[2]

(3)

Controle

een effectieve manier om twe antwoorden t evergelijken voor hetzelfde probleem is het verschil te berekenen van een vergelijking met de twee integralen

#lhs(%);

#rhs(%%);

 

#diff(lhs(%)-rhs(%)=0,x);

NULL

#diff(f,x);

diff(lhs(%)-rhs(%)=0,x);

(x^2+1)^(1/2)-(1/4)*(x+(x^2+1)^(1/2))*(1+x/(x^2+1)^(1/2))-(1/2)*(1+x/(x^2+1)^(1/2))/(x+(x^2+1)^(1/2))-(1/4)*(1+x/(x^2+1)^(1/2))/(x+(x^2+1)^(1/2))^3 = 0

(4)

simplify(%);

0 = 0

(5)

Strange that  diff(lhs(%)-rhs(%)=0,x);  is translated by 2 d input with round d notation for functions with two variables ?
The two integrals are functions of one variable
diff(f, x)

Download Controleren_dezelfde_antwoord_voo_expressies.mw

Sometimes its easier when doing math in maple input mode to use first the 2d maple input mode and convert this to maple input
Is there a hotkey assigned in Maple to do this toggling from 1d input to 2d input ( also from 1d output to 2d output  )

Now it must be done by mouse

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