diff --git a/src/area_shape.h b/src/area_shape.h
index 22d1904..1515f08 100644
--- a/src/area_shape.h
+++ b/src/area_shape.h
@@ -158,7 +158,7 @@ double trapezoidArea(double largerBase, double smallerBase, double height)
 double regularPolygonArea(double side, int nOfSides)
 {
   double apothen, perimeter, result;
-  assert(side > 0 && nOfSides > 0);
+  assert(side > 0 && nOfSides >= 3);
   apothen = side / (2 * tan(M_PI / nOfSides));
   perimeter = side * nOfSides;
   result = perimeter * apothen / 2;
diff --git a/src/geometry.h b/src/geometry.h
index a6ec2d2..1ac8b8d 100644
--- a/src/geometry.h
+++ b/src/geometry.h
@@ -79,7 +79,7 @@ double *midpointPoints(double ax, double ay, double bx, double by)
 double slopeOfLine(double x1, double y1, double x2, double y2)
 {
   double result;
-  assert(x1 != x2 || y1 != y2);
+  assert(x1 != x2);
   result = (y2 - y1) / (x2 - x1);
   return result;
 }
@@ -156,7 +156,7 @@ double circlePerimeter(double radius)
 int nOfDiagnonalsPolygon(int nOfSides)
 {
   double result;
-  assert(nOfSides > 0);
+  assert(nOfSides >= 3);
   result = nOfSides * (nOfSides - 3) / 2;
   return result;
 }
@@ -171,7 +171,7 @@ int nOfDiagnonalsPolygon(int nOfSides)
 double convexPolygonSumInteriorAngles(double nOfSides)
 {
   double result;
-  assert(nOfSides > 0);
+  assert(nOfSides >= 3);
   result = (nOfSides - 2) * M_PI;
   return result;
 }
@@ -187,7 +187,7 @@ double convexPolygonSumInteriorAngles(double nOfSides)
 double regularPolygonInteriorAngle(int nOfSides)
 {
   double result;
-  assert(nOfSides > 0);
+  assert(nOfSides >= 3);
   result = convexPolygonSumInteriorAngles(nOfSides) / nOfSides;
   return result;
 }
@@ -202,7 +202,7 @@ double regularPolygonInteriorAngle(int nOfSides)
 double convexPolygonExteriorAngle(int nOfSides)
 {
   double result;
-  assert(nOfSides > 0);
+  assert(nOfSides >= 3);
   result = 2 * M_PI / nOfSides;
   return result;
 }
diff --git a/src/test/main.c b/src/test/main.c
index 172e8ee..73e5207 100644
--- a/src/test/main.c
+++ b/src/test/main.c
@@ -255,6 +255,10 @@ int main()
   test(185, round(radians2degrees(regularPolygonInteriorAngle(6))) == 120);
   test(186, round(radians2degrees(convexPolygonExteriorAngle(5))) == 72);
   test(187, round(radians2degrees(convexPolygonExteriorAngle(6))) == 60);
+  test(188, nOfDiagnonalsPolygon(3) == 0);
+  test(189, round(radians2degrees(convexPolygonSumInteriorAngles(3))) == 180);
+  test(190, round(radians2degrees(regularPolygonInteriorAngle(3))) == 60);
+  test(191, round(radians2degrees(convexPolygonExteriorAngle(3))) == 120);
 
   puts("Passed all tests successfully!");
 
diff --git a/src/trigonometry.h b/src/trigonometry.h
index 9a14f6a..a7558ef 100644
--- a/src/trigonometry.h
+++ b/src/trigonometry.h
@@ -29,7 +29,7 @@ double hypotenuse(double sideA, double sideB)
 double sideRightTriangle(double hypotenuse, double sideA)
 {
   double result;
-  assert(sideA > 0 && hypotenuse > 0);
+  assert(sideA > 0 && hypotenuse > sideA);
   result = sqrt(pow(hypotenuse, 2) - pow(sideA, 2));
   return result;
 }