implement cot as tan(pi/2 - angle)

glm/gtc/reciprocal.inl

@@ -66,7 +66,9 @@ namespace glm
 	GLM_FUNC_QUALIFIER genType cot(genType angle)
 	{
 		GLM_STATIC_ASSERT(std::numeric_limits<genType>::is_iec559, "'cot' only accept floating-point values");
-		return genType(1) / glm::tan(angle);
+		genType const pi_over_2 = genType(3.1415926535897932384626433832795 / 2.0);
+		
+		return glm::tan(pi_over_2 - angle);
 	}
 
 	template <typename T, precision P, template <typename, precision> class vecType>