# HG changeset patch
# User Karl-Dieter Crisman <kcrisman@gmail.com>
# Date 1274975156 14400
# Node ID a4a7a2386364dbced964bb66ecb68449c824e6d8
# Parent d3bb1a7a0ac49eccad3ea4053f938a3518c403ed
Trac 8568 - implement derivative for erf and ensure only legal symbolic derivatives are converted to Maxima
diff --git a/sage/functions/other.py b/sage/functions/other.py
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| 79 | 79 | raise NotImplementedError, "erf not implemented for precision higher than 53" |
| 80 | 80 | return parent(1 - pari(float(x)).erfc()) |
| 81 | 81 | |
| | 82 | def _derivative_(self, x, diff_param=None): |
| | 83 | """ |
| | 84 | Derivative of erf function |
| | 85 | |
| | 86 | EXAMPLES:: |
| | 87 | |
| | 88 | sage: erf(x).diff(x) |
| | 89 | 2*e^(-x^2)/sqrt(pi) |
| | 90 | |
| | 91 | TESTS:: |
| | 92 | |
| | 93 | Check if #8568 is fixed:: |
| | 94 | |
| | 95 | sage: var('c,x') |
| | 96 | (c, x) |
| | 97 | sage: derivative(erf(c*x),x) |
| | 98 | 2*c*e^(-c^2*x^2)/sqrt(pi) |
| | 99 | sage: erf(c*x).diff(x)._maxima_init_() |
| | 100 | '((%pi)^(-1/2))*(c)*(exp(((c)^(2))*((x)^(2))*(-1)))*(2)' |
| | 101 | """ |
| | 102 | return 2*exp(-x**2)/sqrt(pi) |
| | 103 | |
| 82 | 104 | erf = Function_erf() |
| 83 | 105 | |
| 84 | 106 | class Function_abs(GinacFunction): |
