diff --git a/C# Full Course for free/5.arithmetic.md b/C# Full Course for free/5.arithmetic.md
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+# Arithmetics
+
+## additions
+
+```C#
+int friends = 5;
+friends = friends + 1;
+friends++;
+```
+
+## substrack
+
+```C#
+friends = friends - 1;
+friends -=  1;
+```
+
+## multiplications
+
+```C#
+friends = friends * 2;
+friends *= 2;
+```
+
+## division
+
+```C#
+friends = friends / 2;
+friends /= 2;
+```
+
+## modulus
+
+```C#
+friends = friends % 3;
+```
+
diff --git a/C# Full Course for free/6.Math Class.md b/C# Full Course for free/6.Math Class.md
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+# Math Class
+
+## Pow
+
+raise to the power of x
+
+```C#
+double a = 3;
+double b = Math.Pow(a,2);
+```
+
+## Sqrt
+
+for the squqre Root
+
+```C#
+double a = 3;
+double b = Math.Sqrt(a);
+```
+
+## Abs
+
+for the absolute value
+
+```C#
+double a = -3;
+double b = Math.Abs(a);
+```
+
+## round
+
+Round a numeber
+
+```C#
+double a = 3.14;
+double b = Math.Round(a);
+```
+
+## Ceiling
+
+round up
+
+```C#
+double a = 3.14;
+double b = Math.Ceilling(a);
+```
+
+## Floor
+
+round down
+
+```C#
+double a = 3.99;
+double b = Math.Floor(a);
+```
+
+## Max
+
+find the max value
+```C#
+double a = 3.99;
+double x = 5;
+double b = Math.Max(a,x);
+```
+## Min
+
+find the min value
+```C#
+double a = 3.99;
+double x = 5;
+double b = Math.Min(a,x);
+```
+
+## Random
+
+Generate a random Number
+
+```C#
+Random random = new Random();
+
+// for int
+int num = random.Next(1, 7);
+
+// for Double
+double num  = radom.NextDouble();
+```
diff --git a/C# Full Course for free/7.hypotenuse_calculator.md b/C# Full Course for free/7.hypotenuse_calculator.md
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+# hypotenuse calculator
+
+in this project we will cover how to implement 
+the hypotenuse theorem
+
+$$
+a^2 + b^2 = c^2
+$$