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I have the following formula:

s'[t] == 230.94 Tan[0.914743 - 0.138564 t]

When I solve this by hand I get:

s[t] == 1666.67*Log[Cos[0.914743-0.138564t]] + c

But Mathematica just returns:

DSolve[s'[t] == 230.94 Tan[0.914743 - 0.138564 t], s[t], t]

s[t] == Integral[ 230.94 Tan[ 0.914743 - 0.138564t ]dt ] + c

Do you know why it isn't solving the integral?

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  • $\begingroup$ What's worse, when you make the numbers rational (e.g., 914743/1000000 instead of the constant term in the Tan), Mathematica just hangs! $\endgroup$
    – Igor Rivin
    Commented Sep 11, 2014 at 21:31

1 Answer 1

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DSolve[s'[t] == (a Tan[b - c t]), s[t], t] /. {a -> 230.94, b -> 0.914743, c -> 0.138564`}

(* {{s[t] -> C[1] + 1666.67 Log[Cos[0.914743 - 0.138564 t]]}} *)
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  • $\begingroup$ this is a good work around, but the OP is certainly seeing a bug... $\endgroup$
    – Igor Rivin
    Commented Sep 11, 2014 at 22:15
  • $\begingroup$ you should read my comment to the OP. $\endgroup$
    – Igor Rivin
    Commented Sep 11, 2014 at 22:23

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