1 files changed, 12 insertions, 0 deletions
diff --git a/src/pj_tsfn.c b/src/pj_tsfn.c
new file mode 100644
index 00000000..3c223e05
--- /dev/null
+++ b/src/pj_tsfn.c
@@ -0,0 +1,12 @@
+/* determine small t */
+#ifndef lint
+static const char SCCSID[]="@(#)pj_tsfn.c	4.3	93/06/12	GIE	REL";
+#endif
+#include <math.h>
+#define HALFPI		1.5707963267948966
+	double
+pj_tsfn(double phi, double sinphi, double e) {
+	sinphi *= e;
+	return (tan (.5 * (HALFPI - phi)) /
+	   pow((1. - sinphi) / (1. + sinphi), .5 * e));
+}