xpressn.c: asinh, acosh, atanh replacement functions added

13 years ago · e5e08b6f93
1 changed files with 12 additions and 0 deletions
--- a/src/frontend/numparam/xpressn.c
+++ b/src/frontend/numparam/xpressn.c
@ -184,13 +184,25 @@ mathfunction(int f, double z, double x)
        y = atan(x);
        break;
    case 31:
+#ifdef HAVE_ASINH
        y = asinh(x);
+#else
+        y = ((x > 0) ? log(x + sqrt(x * x + 1.0)) : -log(-x + sqrt(x * x + 1.0)));
+#endif
        break;
    case 32:
+#ifdef HAVE_ACOSH
        y = acosh(x);
+#else
+        y = (log(x + sqrt(x*x-1.0)));
+#endif
        break;
    case 33:
+#ifdef HAVE_ATANH
        y = atanh(x);
+#else
+        y = (log((1.0 + x) / (1.0 - x)) / 2.0);
+#endif
        break;
    case 34:
        y = tan(x);