## 564 Reputation

6 years, 345 days

## a problem with fsolve...

Maple

i have a problem with a nonlinear equation containing Heaviside step function. fsolve does not return anything and SolveEquation command also returns incorrect answer. How can i solve this equation? any method or help is appreciated.

 >
 > restart:
 > with(DirectSearch):
 > F:=x*(Heaviside(x-(S0))/(1-DD)+Heaviside(-x+S0)/(1-HH*DD));
 (1)
 > EQ:=F-E*Y;
 (2)
 > HH:=0.2; DD:=0.579350262599427; S0:=1e8; E:=70e9; Y:=0.001668993263529;
 (3)
 > EQ
 (4)
 > fsolve(EQ)
 (5)
 > SolveEquations(EQ)
 (6)
 > eval(EQ,x = 1.00000000000000*10^8)
 (7)
 >

## A problem related to chain rule derivati...

Maple

i have two expressions. S1 and S2 are functions of sigma and tau. but i need derivative of sigma and tau with respect to S1 and S2. what should i do ? could any one help?

 > restart
 > S1 := -4*sqrt(sigma1^2 + 4*tau^2)*tau^2/((sigma1 + sqrt(sigma1^2 + 4*tau^2))^2*(1 + 4*abs(tau/(sigma1 + sqrt(sigma1^2 + 4*tau^2)))^2))
 (1)
 > S2 := 4*sqrt(sigma1^2 + 4*tau^2)*tau^2/((-sigma1 + sqrt(sigma1^2 + 4*tau^2))^2*(1 + 4*abs(tau/(-sigma1 + sqrt(sigma1^2 + 4*tau^2)))^2))
 (2)
 >
 >
 >

## Linear composition of vectors...

Maple

Hi. how can maple determine whether a vector is linear compostion of two or more vectors?
for example w=a*v+b*u so that w is linear compostion of vectors u and v ( a and b are scalar numbers). tnx for the help.

## problem in dsolve...

Maple 2018

i have two ode equations, when try to solve, i face this error
Error, (in dsolve/numeric/bvp/convertsys) unable to convert to an explicit first-order system
any comment or help to solve this? ( or any simplifying comments to solve) . thnx in advance

 > restart
 > A := 4263736263.736263:B := 11868131.86813187:C := 600146.5201465202:hr := 0.3e7:muz := 0.2632654643708247e-5:P:=1000:
 (1)
 > ode1 := diff(u(r), r, r)+(diff(u(r), r))/r-u(r)/r^2-B*(diff(w(r), r, r, r)+(diff(w(r), r, r))/r-(diff(w(r), r))/r^2)/A = 0;
 (2)
 > ode2 := C*(diff(w(r), r, r, r, r))+2*C*(diff(w(r), r, r, r))/r-(C/r^2+muz*hr^2)*(diff(w(r), r, r))+(C/r^3-muz*hr^2/r)*(diff(w(r), r))+muz*hr^2*w(r)/r^2-B*(diff(u(r), r, r, r))-2*B*(diff(u(r), r, r))/r+B*(diff(u(r), r))/r^2-B*u(r)/r^3 = P;
 (3)
 > ics := w(.2) = 0, (D(w))(.2) = 0, w(1) = 0, (D(w))(1) = 0, u(.2) = 0, u(1) = 0;
 (4)
 > dsolve({ode1,ode2} union {ics},{w(r),u(r)},numeric)
 >
 >

## problem with int...

Maple

i want to solve an integration as a funstion of T, but it return the integral unevaluated, but when i change the place of "numeric option" it returns sth. what is the problem ?

 > restart:with(RealDomain):
 > simplify((2/pi)^(1/2)*(int((exp(-32.74123792568-0.8916456579806e-1*ln(4.852623952*10^9*v^2)))*exp(-v^2/(2*T))*v^3, v = 2 .. 100,numeric,AllSolutions)))
 (1)
 > simplify((2/pi)^(1/2)*(int((exp(-32.74123792568-0.8916456579806e-1*ln(4.852623952*10^9*v^2)), numeric)*exp(-v^2/(2*T))*v^3, v = 2 .. 100)), AllSolutions);
 (2)
 >