[_separable]
Book solution method
Separable ODE, Neither variable missing
Mathematica ✓
cpu = 0.127647 (sec), leaf count = 321
Maple ✓
cpu = 0.015 (sec), leaf count = 28
DSolve[(1 + x^2)^(3/2)*(y[x] + Sqrt[1 + y[x]^2])*y'[x] == 1 + y[x]^2,y[x],x]
Mathematica raw output
{{y[x] -> ((-I)*(-1 + Cosh[x/Sqrt[1 + x^2] + C[1]] + Sinh[x/Sqrt[1 + x^2] + C[1]
]))/Sqrt[1 - 2*Cosh[x/Sqrt[1 + x^2] + C[1]] - 2*Sinh[x/Sqrt[1 + x^2] + C[1]]]},
{y[x] -> (I*(-1 + Cosh[x/Sqrt[1 + x^2] + C[1]] + Sinh[x/Sqrt[1 + x^2] + C[1]]))/
Sqrt[1 - 2*Cosh[x/Sqrt[1 + x^2] + C[1]] - 2*Sinh[x/Sqrt[1 + x^2] + C[1]]]}, {y[x
] -> ((-I)*(1 + Cosh[x/Sqrt[1 + x^2] + C[1]] + Sinh[x/Sqrt[1 + x^2] + C[1]]))/Sq
rt[1 + 2*Cosh[x/Sqrt[1 + x^2] + C[1]] + 2*Sinh[x/Sqrt[1 + x^2] + C[1]]]}, {y[x]
-> (I*(1 + Cosh[x/Sqrt[1 + x^2] + C[1]] + Sinh[x/Sqrt[1 + x^2] + C[1]]))/Sqrt[1
+ 2*Cosh[x/Sqrt[1 + x^2] + C[1]] + 2*Sinh[x/Sqrt[1 + x^2] + C[1]]]}}
Maple raw input
dsolve((y(x)+(1+y(x)^2)^(1/2))*(x^2+1)^(3/2)*diff(y(x),x) = 1+y(x)^2, y(x),'implicit')
Maple raw output
1/(x^2+1)^(1/2)*x-arcsinh(y(x))-1/2*ln(1+y(x)^2)+_C1 = 0