diff --git a/README.md b/README.md
index 7ddb52d..5569304 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,10 @@ My goal for this project is to write an open sourced mathmatical library for C a
 ## List of calculators
 
 - Hypotenuse calculator (a²+b²=c²)
+- Circumference of a Circle
 - Area of a circle (πr²)
+- Area of a Triangle
+- Area of a Rectangle
 - Matrix arithmetics (2-D arrays)
     - Determinant of 2*2 matrix
     - Scalar multiplication
@@ -28,11 +31,4 @@ My goal for this project is to write an open sourced mathmatical library for C a
     - Determinant of n*n matrix
     - Matrix support for none integer numbers
 - Derivative
-- Integral
-- Area
-    - Area of a triangle
-    - Area of a quadralateral
-- Peremeter
-    - Peremeter of a triangle
-    - Peremeter of a quadralateral
-    - Circumference of a circle
\ No newline at end of file
+- Integral
\ No newline at end of file
diff --git a/formulas.h b/formulas.h
index bdc9ec7..0c6f9df 100644
--- a/formulas.h
+++ b/formulas.h
@@ -29,4 +29,19 @@ double areaOfCircle(double radius)
     area = acos(-1) * pow(radius, 2);
 
     return area;
-}
\ No newline at end of file
+};
+
+double areaOfTriangle(double height, double base)
+{
+    return (height * base)*(1.0/2.0);
+};
+
+double areaOfRectangle(double height, double base)
+{
+    return (height * base);
+};
+
+double circumferenceOfCircle(double radius)
+{
+    return (2 * acos(-1) * radius);
+};
\ No newline at end of file
diff --git a/main.c b/main.c
index 9d9c5fd..7f8bf4f 100644
--- a/main.c
+++ b/main.c
@@ -18,6 +18,8 @@ int main()
     printf("\n  6. * Matrix multiplication *");
     printf("\n  7. Scalar matrix multiplication");
     printf("\n  8. Exponent");
+    printf("\n  9. Area of Triangle");
+    printf("\n  10. Area of Rectangle");
 
     printf("\n\n * Stared entries are not fully programmed.");
     printf("\n Enter your choice here:_____");
@@ -133,8 +135,7 @@ int main()
 
         system("clear");
         printf("\n ~~ Exponenet ~~\n\n");
-        double base;
-        double exp;
+        double base, exp;
         printf("\nPlease enter the base: ");
         scanf("%lf", &base);
         printf("\nPlease enter the exponent: ");
@@ -143,6 +144,43 @@ int main()
         printf("%lf to the power of %lf is equal to %lf.\n", base, exp, num);
 
         break;
+    
+    case 9:
+        system("clear");
+        printf("\n ~~ Area of Triangle ~~\n\n");
+        double triBase, triHeight;
+        printf("\nPlease enter the base: ");
+        scanf("%lf", &triBase);
+        printf("\nPlease enter the height: ");
+        scanf("%lf", &triHeight);
+        double triArea = areaOfTriangle(triHeight, triBase);
+        printf("The area of triangle is %lf.\n", triArea);
+
+        break;
+
+    case 10:
+        system("clear");
+        printf("\n ~~ Area of Rectangle ~~\n\n");
+        double recBase, recHeight;
+        printf("\nPlease enter the base: ");
+        scanf("%lf", &recBase);
+        printf("\nPlease enter the height: ");
+        scanf("%lf", &recHeight);
+        double recArea = areaOfRectangle(recHeight, recBase);
+        printf("The area of rectangle is %lf.\n", recArea);
+
+        break;
+        
+    case 11:
+        system("clear");
+        printf("\n ~~ Circumference of a Circle ~~\n\n");
+        double  cirRadius;
+        printf("\nPlease enter the radius: ");
+        scanf("%lf", &cirRadius);
+        double circumference = circumferenceOfCircle(cirRadius);
+        printf("The circumference is %lf.\n", circumference);
+
+        break;
 
     default:
         printf("\n Incorrect input, try again.\n");