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diff --git a/src/c/signalProcessing/%sn/dmodsns.c b/src/c/signalProcessing/%sn/dmodsns.c
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+++ b/src/c/signalProcessing/%sn/dmodsns.c
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+/* Copyright (C) 2017 - IIT Bombay - FOSSEE
+
+ This file must be used under the terms of the CeCILL.
+ This source file is licensed as described in the file COPYING, which
+ you should have received as part of this distribution.  The terms
+ are also available at
+ http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
+ Author: Ankit Raj
+ Organization: FOSSEE, IIT Bombay
+ Email: toolbox@scilab.in
+ Reference:- Abramowitz, Milton and Stegun, Irene A
+             Handbook of Mathematical Functions, Dover, 1965
+             Chapter 16 (Sections 16.4, 16.13 and 16.15)
+	Link for FORTRAN code:-http://www.aip.de/groups/soe/local/numres/bookfpdf/f6-11.pdf
+*/
+
+#include<stdio.h>
+#include<math.h>
+#define CA 0.0003
+#include "modsn.h"
+double dmodsns(double uu, double emmc)
+{
+	double a,b,c,d,emc,u;
+	double em[14],en[14];
+	int i,ii,l,bo;
+	double sn,cn,dn;
+	emc=1-emmc;
+	u=uu;
+	if(emc)
+	{
+	bo=(emc<0.0);
+		if(bo)
+		{
+			d=1.0-emc;
+			emc/=-1.0/d;
+			u*=(d=sqrt(d));
+		}
+		a=1.0;
+		dn=1.0;
+		for(i=1;i<=13;i++)
+		{
+			l=i;
+			em[i]=a;
+			en[i]=(emc=sqrt(emc));
+			c=0.5*(a+emc);
+			if(fabs(a-emc)<=CA*a)break;
+			emc*=a;
+			a=c;
+		}
+		u*=c;
+		sn=sin(u);
+		cn=cos(u);
+		if(sn)
+		{
+			a=cn/sn;
+			c*=a;
+			for(ii=l;ii>=1;ii--)
+			{
+				b=em[ii];
+				a*=c;
+				c*=dn;
+				dn=(en[ii]+a)/(b+a);
+				a=c/b;
+			}
+			a=1.0/sqrt(c*c+1.0);
+			sn=(sn>=0.0?a:-a);
+			cn=c*(sn);
+		}
+		if(bo)
+		{
+			a=dn;
+			dn=cn;
+			cn=a;
+			sn/=d;
+		}
+	}
+	else
+	{
+		cn=1.0/cosh(u);
+		dn=cn;
+		sn=tanh(u);
+	}
+	return sn;
+}
+/*
+int main()
+{
+	double u,k;
+	u=4;
+	k=0.7;
+	sn(u,k);
+}
+*/