Add cmath header

include_std/cmath

@@ -0,0 +1,37 @@
+/*
+   This file is part of Fennix Kernel.
+
+   Fennix Kernel is free software: you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation, either version 3 of
+   the License, or (at your option) any later version.
+
+   Fennix Kernel is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+namespace std
+{
+	double sin(double x)
+	{
+		const int NUM_TERMS = 10;
+
+		double result = 0.0;
+		double term = x;
+
+		for (int i = 1; i <= NUM_TERMS; ++i)
+		{
+			result += term;
+			term *= -x * x / ((2 * i) * (2 * i + 1));
+		}
+
+		return result;
+	}
+}