Good evening everybody!

Unfortunately, I didn't manage to draw the graph of the difference of two interpolating functions, that were received as numerical solution of two ODEs.

Some typical methods, such as ordinary "-" and some combinations with these functions didn't help.

Thanks beforehand.

r := 0.1;

c := 1/r;

c1 := 0.01;

a := 1; b := 0;

s = NDSolve[{Z''[z] + r*(-c1*Sin[z]*Exp[-z/r] + c)*Z[z] == 0,

Z[b] == 0, Z'[0] == a}, Z[z], {z, 0, 100}];

s1 = NDSolve[{Y''[z] + r*c*Y[z] == 0, Y[b] == 0, Y'[0] == a},

Y[z], {z, 0, 100}];

nsol[z_]: = (Z[z] /. (s[[1]][[1]])) - (Y[z] /. (s1[[1]][[1]]));

Plot[nsol[z], {z, 0, 100}]