diff --git a/src/decn/decn_tests_trig.cpp b/src/decn/decn_tests_trig.cpp
index ddac974..f3b618a 100644
--- a/src/decn/decn_tests_trig.cpp
+++ b/src/decn/decn_tests_trig.cpp
@@ -6,83 +6,60 @@
 namespace bmp = boost::multiprecision;
 using Catch::Matchers::Equals;
 
+
+static void trig_test(void (*operation)(void), bmp::mpfr_float (*mpfr_operation)(bmp::mpfr_float x),
+	const char* a_str, int a_exp, double rtol, double atol)
+{
+	CAPTURE(a_str); CAPTURE(a_exp);
+	build_dec80(a_str, a_exp);
+	operation();
+	decn_to_str_complete(&AccDecn);
+	CAPTURE(Buf);
+
+	bmp::mpfr_float::default_precision(50);
+	std::string a_full_str(a_str);
+	a_full_str += "e" + std::to_string(a_exp);
+
+	bmp::mpfr_float a_actual(a_full_str);
+	a_actual = mpfr_operation(a_actual);
+	CAPTURE(a_actual);
+
+	bmp::mpfr_float calculated(Buf);
+	if (rtol >= 0) {
+		bmp::mpfr_float rel_diff = abs((a_actual - calculated) / a_actual);
+		CHECK(rel_diff < rtol);
+	} else {
+		bmp::mpfr_float diff = abs(a_actual - calculated);
+		CHECK(diff < atol);
+	}
+
+}
+
 static void sin_test(
 	const char* a_str, int a_exp, double rtol=5e-3, double atol=1e-3)
 {
-	CAPTURE(a_str); CAPTURE(a_exp);
-	build_dec80(a_str, a_exp);
-	sin_decn();
-	decn_to_str_complete(&AccDecn);
-	CAPTURE(Buf);
-
-	bmp::mpfr_float::default_precision(50);
-	std::string a_full_str(a_str);
-	a_full_str += "e" + std::to_string(a_exp);
-
-	bmp::mpfr_float a_actual(a_full_str);
-	a_actual = sin(a_actual);
-	CAPTURE(a_actual);
-
-	bmp::mpfr_float calculated(Buf);
-	if (rtol >= 0) {
-		bmp::mpfr_float rel_diff = abs((a_actual - calculated) / a_actual);
-		CHECK(rel_diff < rtol);
-	} else {
-		bmp::mpfr_float diff = abs(a_actual - calculated);
-		CHECK(diff < atol);
-	}
+	trig_test(sin_decn, [](bmp::mpfr_float x) -> bmp::mpfr_float {return sin(x);}, a_str, a_exp, rtol, atol);
 }
 
 static void cos_test(
-	const char* a_str, int a_exp, double rtol=1e-2)
+	const char* a_str, int a_exp, double rtol=5e-3, double atol=1e-3)
 {
-	CAPTURE(a_str); CAPTURE(a_exp);
-	build_dec80(a_str, a_exp);
-	cos_decn();
-	decn_to_str_complete(&AccDecn);
-	CAPTURE(Buf);
-
-	bmp::mpfr_float::default_precision(50);
-	std::string a_full_str(a_str);
-	a_full_str += "e" + std::to_string(a_exp);
-
-	bmp::mpfr_float a_actual(a_full_str);
-	a_actual = cos(a_actual);
-	CAPTURE(a_actual);
-
-	bmp::mpfr_float calculated(Buf);
-	bmp::mpfr_float rel_diff = abs((a_actual - calculated) / a_actual);
-
-	CHECK(rel_diff < rtol);
+	trig_test(cos_decn, [](bmp::mpfr_float x) -> bmp::mpfr_float {return cos(x);}, a_str, a_exp, rtol, atol);
 }
 
 static void tan_test(
-	const char* a_str, int a_exp, double rtol=1e-2, double atol=1e-3)
+	const char* a_str, int a_exp, double rtol=5e-3, double atol=1e-3)
 {
-	CAPTURE(a_str); CAPTURE(a_exp);
-	build_dec80(a_str, a_exp);
-	tan_decn();
-	decn_to_str_complete(&AccDecn);
-	CAPTURE(Buf);
-
-	bmp::mpfr_float::default_precision(50);
-	std::string a_full_str(a_str);
-	a_full_str += "e" + std::to_string(a_exp);
-
-	bmp::mpfr_float a_actual(a_full_str);
-	a_actual = tan(a_actual);
-	CAPTURE(a_actual);
-
-	bmp::mpfr_float calculated(Buf);
-	if (rtol >= 0) {
-		bmp::mpfr_float rel_diff = abs((a_actual - calculated) / a_actual);
-		CHECK(rel_diff < rtol);
-	} else {
-		bmp::mpfr_float diff = abs(a_actual - calculated);
-		CHECK(diff < atol);
-	}
+	trig_test(tan_decn, [](bmp::mpfr_float x) -> bmp::mpfr_float {return tan(x);}, a_str, a_exp, rtol, atol);
 }
 
+
+const char * const pi = "3.141592653589793239";
+const char * const pi_threequarters = "2.356194490192344929";
+const char * const pi_halfed = "1.570796326794896619";
+const char * const pi_quarted = ".7853981633974483096";
+
+
 TEST_CASE("sin") {
 	sin_test("0.1", 0);
 	sin_test("0.05", 0);
@@ -100,6 +77,10 @@ TEST_CASE("sin") {
 	sin_test("2.0", 0);
 	sin_test("2.5", 0);
 	sin_test("3.0", 0);
+	sin_test(pi, 0, -1);
+	sin_test(pi_quarted, 0);
+	sin_test(pi_halfed, 0);
+	sin_test(pi_threequarters, 0);
 }
 
 TEST_CASE("cos") {
@@ -119,6 +100,10 @@ TEST_CASE("cos") {
 	cos_test("2.0", 0);
 	cos_test("2.5", 0);
 	cos_test("3.0", 0);
+	cos_test(pi, 0);
+	cos_test(pi_quarted, 0);
+	cos_test(pi_halfed, 0, -1);
+	cos_test(pi_threequarters, 0);
 }
 
 
@@ -126,9 +111,9 @@ TEST_CASE("tan") {
 	tan_test("0.1", 0);
 	tan_test("0.05", 0);
 	tan_test("0.01", 0);
-	tan_test("0.001", 0);
-	tan_test("0.0001", 0);
-	tan_test("0.00001", 0);
+	tan_test("0.001", 0, -1);
+	tan_test("0.0001", 0, -1);
+	tan_test("0.00001", 0, -1);
 	tan_test("0.000001", 0, -1);
 	tan_test("0.0", 0, -1);
 	tan_test("0.2", 0);