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I'm not sure why im getting a complex solution for evalf(h(-1/2)). Posted screenshot here:

http://prntscr.com/8abmta

The answer should be positive 6*2^(2/3) ≈ 9.52

 The computer returns

h(-1/2) =

=

The problem is that evalf((-1)^(1/3)) you get 0.500 + .866I

Is there no way to evaluate a second derivative of a real valued function which has a fractional exponent without receiving complex results? I don't have the time to look at each function and try to figure out what went wrong. I want to plug in any x value into a function defined for all reals and get a real result.

I tried  assume(x , 'real' ) , that did not do anything.

 

    

Dear all,

I am trying to solve the following partial differential equation (transport or advection equation) with given initial and boundary conditions:

restart: with(PDEtools):
sys := [v*diff(u(x,t), x) + diff(u(x,t), t) = 0, u(x,0) = exp(-x), u(0,t) = sin(t)];
pdsolve(sys);

But it does not work. The solution is (or should be): 

u(x, t) = exp(t*v-x)+Heaviside(t-x/v)*(sin(t-x/v)-exp(t*v-x))

I think the reason is that the interval for t (in [0, inf)) and x (in [0, 1]) is not specified. On the other hand, this works:

restart: with(PDEtools):
sys := [diff(u(x, t), t) = diff(u(x, t), x, x), u(0, t) = 0, u(1, t) = 0, u(x,0) = f(x)];
sol := pdsolve(sys);

How can I solve a PDE like the transport equation with given initial AND boundary conditions?

Thanks a lot

Cheers!

I'm having a problem with my student work, about to have a solution of 6 equations... Can help me in this file? i dont know how to solve this... this had-me a null solve...

 

 


Thanks for the help =)

restart

M1 := 0.15e5;

0.15e5

 

0.60e5

 

0

 

0.12e5

 

21000.00000

 

3

 

1

 

2.5

 

1

 

3

(1)

`σadm` := 175*10^6;

175000000

 

(1/300000)*L

 

210000000000

(2)

Atria := (3.5*12)/(LBC+LCD)

12.00000000

(3)

Ctria := LAB+LBC+(1/3)*(2*(LCD+LDE))

6.333333334

(4)

AiXil := Atria*Ctria

76.00000001

(5)

C := AiXil/Atria

6.333333334

(6)

``

``

``

SumFX := FAx;

FAx

(7)

SumFY := FAy+FCy+FEy-F5-QTria;

FAy+FCy+FEy-81000.00000

(8)

SumMA := FCy*(LAB+LBC)-F5*(LAB+LBC)+FEy*(LAB+LBC+LCD+LDE)+M1-MA-QTria*Ctria;

4*FCy-358000.0000+7.5*FEy-MA

(9)

NULL

``

``

EIYac := EIYo+`EIθo`*x+M1*(x+0)^3/factorial(3);

EIYo+`EIθo`*x+2500.000000*x^3

(10)

EIYce := EIYac+FCy*(x-4)^3/factorial(3)-F5*(x-4)^3/factorial(3)-q5*(x-4)^5/((3.5)*factorial(5));

EIYo+`EIθo`*x+2500.000000*x^3+(1/6)*FCy*(x-4)^3-10000.00000*(x-4)^3-28.57142857*(x-4)^5

(11)

EIYef := EIYce+FEy*(x-7.5)^3/factorial(3)+(1/3)*q5*(x-7.5)^5/factorial(5);

EIYo+`EIθo`*x+2500.000000*x^3+(1/6)*FCy*(x-4)^3-10000.00000*(x-4)^3-28.57142857*(x-4)^5+(1/6)*FEy*(x-7.5)^3+33.33333333*(x-7.5)^5

(12)

`EIθac` := diff(EIYac, x);

`EIθo`+7500.000000*x^2

(13)

`EIθce` := diff(EIYce, x);

`EIθo`+7500.000000*x^2+(1/2)*FCy*(x-4)^2-30000.00000*(x-4)^2-142.8571428*(x-4)^4

(14)

`EIθef` := diff(EIYef, x);

`EIθo`+7500.000000*x^2+(1/2)*FCy*(x-4)^2-30000.00000*(x-4)^2-142.8571428*(x-4)^4+(1/2)*FEy*(x-7.5)^2+166.6666666*(x-7.5)^4

(15)

``

Mac := diff(`EIθac`, x);

15000.00000*x

(16)

Mce := diff(`EIθce`, x);

-45000.00000*x+FCy*(x-4)+240000.0000-571.4285712*(x-4)^3

(17)

Mef := diff(`EIθef`, x);

-45000.00000*x+FCy*(x-4)+240000.0000-571.4285712*(x-4)^3+FEy*(x-7.5)+666.6666664*(x-7.5)^3

(18)

``

Vac := diff(Mac, x);

15000.00000

(19)

Vce := diff(Mce, x);

-45000.00000+FCy-1714.285714*(x-4)^2

(20)

Vef := diff(Mef, x);

-45000.00000+FCy-1714.285714*(x-4)^2+FEy+1999.999999*(x-7.5)^2

(21)

``

x := 0:
``

`EIθo` = 0

 

EIYo = 0

(22)

x := 4:

EIYo+4*`EIθo`+160000.0000

(23)

x := 7.5:

EIYo+7.5*`EIθo`+610931.2500+7.145833333*FCy

(24)

SOL := solve({CF1, CF2, CF3, CF4, SumFY, SumMA}, {EIyo, FAy, FCy, FEy, MA, `EIyθo`});

"SOL:="

(25)

``

NULL

``

 

Download Equacoes_universais_T12_-_4.mwEquacoes_universais_T12_-_4.mw

Hi, I have a function as following:

50*tan(8*Pi/180)=(a1/(d2-d1))*ln(d2/d1)+(a2/(d3-d2))*ln(d3/d2)+((0.6-a1-a2)/(d4-d3))*ln(d4/d3)

where d1=0.01..0.06, d2>=d1, d3>=d2, d4>=d3, a1>0,a2>0, a1+a2<0.6.

I want to get  all the solutions of d1,d2,d3,d4,a1,a2, which satify the equation and the constrains, is there any way to solve this problem by using maple?

 

 

 

Hello,

This is the system of equations in term of sin and cos. I have used the command "solve" in Maple but it yielded only 2 solutions. I've tried to use with(RealDomain): It yielded more solutions but most of them were wrong.

 

 

f1 := -8100+(-30+70*cos(t1)-40*cos(t2))^2+(-70*sin(t1)+40*sin(t2))^2

f2 := (-20-80*cos(t3))^2+(-15+70*cos(t1)+10*cos(t1+t))^2+(-70*sin(t1)-10*sin(t1+t)+80*sin(t3))^2-5625

f3 := (-20-80*cos(t3))^2+(15+40*cos(t2)+10*cos(t1+t))^2+(-40*sin(t2)-10*sin(t1+t)+80*sin(t3))^2-5625

f4 := 10*cos(t1+t)*(30-70*cos(t1)+40*cos(t2))-10*sin(t1+t)*(70*sin(t1)-40*sin(t2))

 

Anybody know how to solve this system of equations to get the full set of roots?

Thank you very much in advance.

Int(piecewise(t < T1, exp((1/2)*t*(1+2*I-I*sqrt(3))), t < T2, -1000*exp((1/2)*t*(1+2*I-I*sqrt(3)))*(-1/1000+T1-t), T2 <= t, -1000*exp((1/2)*t*(1+2*I-I*sqrt(3)))*(-1/1000-T2+T1)), t)

 

 

Dear's, I am facing some problem to find the particular solution please find the attachment.

Help-1.mw

 

PhD (Scholar)
Department of Mathematics

Hello,

please help check what's wrong with this code. I need the analytic solution and convert to Bessel but return error. Here is the worksheet ID_1.mw

Best regards.

i want to find the stability of this equation, but there is seem to have some problems..can somebody help me..

 

y := A*(1/x+x*exp(-2*sqrt(-1)*b))+4*(exp(h)-1)^2*(2*exp(-sqrt(-1)*b)-3*(exp(h)-1)^2*x^(-exp(h)+1)*exp(sqrt(-1)*b*(-exp(h)+1-1))+3*x^(-exp(h)+1)*exp(sqrt(-1)*b*(-exp(h)+1-1)))/(3*(1-r))-exp(-2*sqrt(-1)*b)/x-x;

subs(A = (1+r)/(1-r), %);

subs(r = (1/3)*(exp(h)-1)^2, %);

subs(b = m*Pi*(exp(h)-1), %);

subs(m = 1, %);

subs(h = 0.5e-1, %);

> ans := solve(%, x);
Warning, solutions may have been lost
ans:=

> r1 := ans[1];
Error, invalid subscript selector
> r2 := ans[2];
Error, invalid subscript selector

Dear all;

Thank you very much for helping me to understand this problem.

I need your help for this question, it's seem for correct but when I run the code there is no dispaly of the solution with this command  dsolve({ode,ics}) ;

 

ode:=x*diff(y(x),x)+y(x)=x*exp(-x^2);

ics:=y(0)=1;

dsolve(ode);

dsolve({ode,ics}) ;

Dear,

 

Last week I made a question, which was kindly answered with the conclusion there might be no solutions.
Now as this cannot be (I'll explain later), I have eliminated all extra aspects of the program to just show the code where the problem is occuring. You can find it via this link prob.mw

The problem is as follows:
I have 3 points, of which I need to determine the distances from the 0,0 point. The distance between the points are known and the angle between the neutral axis and the line through a point are also known. The set-up is shown in the rough sketch. (k1,k2,k3,corner 1, corner 2, corner 3 are known; a,b,c are unknown.). With these values known, I can easily calculate a,b,c via the cosine rule.

However I want to make a sensitivity analysis for a parameter that determines the 3 corners (called f in the code). Herefore I need to become an answer of a,b,c in function of f and only f (as I need them in following calculations which are not shown in the code). However this doesnt seem to work. The program does not return a solution.

Do you guys know how I can make sure that this program is runnable, so I can get my a,b,c values in function of f? I'd be very very very thankful as I'm stuck with this crucial part of my calculation for weeks.

With kind regards
Mathieu

 

Dear,

I have a perfectly working when all parameters are known (figure 1), however I want to perform a sensitivity analysis by derivating the code if one parameter is unknown. Because of multiple possible answers and because of the complexity of the formula, I cannot run this script and get solutions. Any ideas how I can this calculation lighter so it is able to run? Values should be real and positive (so 1 or 2 solutions are the only one I'm interested in)

Any ideas, how I can make this code runnable? (file is below)

I'm stuck on this for a while now :/ So I hope someone will be able to help me

Many thanks in advance!l

Question.mw

Figure 1: [URL=http://s1240.photobucket.com/user/laggstar/media/Parameter%20f%20known.png.html][IMG]http://i1240.photobucket.com/albums/gg494/laggstar/Parameter%20f%20known.png[/IMG][/URL]

 

Figure 2: [URL=http://s1240.photobucket.com/user/laggstar/media/Parameter%20f%20unknown.png.html][IMG]http://i1240.photobucket.com/albums/gg494/laggstar/Parameter%20f%20unknown.png[/IMG][/URL]

 

i asked it to show explanations

and got an solution about that, but it doesnt work in my Maple

i wanna know what do i wrong , why it`s not working right

 

Dear Community Members,

 

We have problem with calculation in Maple v11 and v18. when we make a calculation by using maple v11 and v18, we was not able to get the solution as you see enclosed. when we clicked to "enter + ; ", programme does not run.

 

I currently have a function quadsum(n) that determines the [x,y] solutions of the above equation for an integer n. :

quadsum:= proc(n::nonnegint)
local
k:= 0, mylist:= table(),
x:= isqrt(iquo(n,2)), y:= x, x2:= x^2, y2:= y^2;
if 2*x2 <> n then x:= x+1; x2:= x2+2*x-1; y:= x; y2:= x2; end if;
while x2 <= n do
y:= isqrt(n-x2); y2:= y^2;
if x2+y2 = n then k:= k+1; mylist[k]:= [x,y] end if;
x:= x+1; x2:= x2+2*x-1;
end do;
convert(mylist, list)
end proc:

How would I alter this so that I get [x,y] for n= (5^a).(13^b).(17^c)(29^d) for non-negative integers a,b,c,d?

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