hi all

i have tow equations and i want plot q vs.A , that A change beetwin 0..phi. vn and a are definite and positive.

f is a function of y.

becouse i have a physical problem so infinity can be 20 , and a can be 10 ,

so whit terms , f[infinity]=f[-infinity]=1 and f'[infinity]=f'[-infinity]=0 .

also phiB[y]=q*int(f,y=-infinity..y) , but i want plot q vs phiB[infinity] when phiB[infinity] change between 0..phi

plz plz help me

(diff(f,y))^2-(f[y]^4)/4+q^2/(f[y]^2)+(1+2*q^2)*(f[y]^2)/2=piecewise(y<-a,1/4+2*q^2,-a<y<a,vn*(f[y]^2)-vn+1/4+2*q^2,y>a,1/4+2*q^2);

phiB[infinity]=q*int(f,y=-infinity..infinity):

A:=phiB[infinity]: