Add original unix v6

source/fort/rt1/dcsin.f

@@ -0,0 +1,13 @@
+	function dcsin(z1)
+	double complex dcsin, z1, z2
+	double precision dummy(2), a, b, c, d
+	equivalence (a,z2,dummy(1)), (b,dummy(2))
+
+	z2 = z1
+	c = dexp(b)
+	d = 1.0d0/c
+	b = dcos(a)*(c-d)/2.0d0
+	a = dsin(a)*(c+d)/2.0d0
+	dcsin = z2
+	return
+	end