Automatically Invoke NDSolve if DSolve Fails 

N[DSolve[…]] invokes NDSolve if symbolic evaluation with DSolve fails.

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X sol = DSolve[{y''[x] + E^(-x) y'[x] + Sin[y[x]] == 1, y[0] == 1, y'[0] == 1}, y, {x, 0, 5}]

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X nsol = N[sol]

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X Table[y[x] /. nsol[[1]], {x, 0, 5}]

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Obtain a numerical solution with higher precision.

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X nprecsol = N[sol, 20]

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X Table[y[x] /. nprecsol[[1]], {x, 0, 5}]

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Obtain a numerical solution for an ODE with symbolic parameters.

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X psol = DSolveValue[{y''[x] + E^(-a x) y'[x] + Sin[y[x]] == b Cos[x], y[0] == 1, y'[0] == 1}, y, {x, 0, 30 \[Pi]}]

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X npsol = N[psol]

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X Plot[Evaluate[Table[npsol[a, b][x], {a, 1, 12, 3}, {b, 1, 3}]], {x, 0, 8 \[Pi]}]

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