From ca962a4ac40875f49a5c415d1e2e1a4d42d8e2d8 Mon Sep 17 00:00:00 2001
From: Chrea Chanchhunneng <chreachanchhunneng@gmail.com>
Date: Thu, 18 Sep 2025 16:13:16 -0500
Subject: [PATCH 1/2] Add triangle

---
 geometry/geometry.py | 50 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/geometry/geometry.py b/geometry/geometry.py
index a0be8eb3befc..2c7ee0f1f556 100644
--- a/geometry/geometry.py
+++ b/geometry/geometry.py
@@ -284,5 +284,55 @@ def area(self) -> float:
         return super().area()
 
 
+class Triangle(Polygon):
+    """
+    A geometric triangle on a 2D surface.
+
+    >>> triangle = Triangle(3, 4, 5)
+    >>> triangle.perimeter()
+    12
+    >>> triangle.area()
+    6.0
+    >>> Triangle(-3, 4, 5)
+    Traceback (most recent call last):
+        ...
+    TypeError: length must be a positive numeric value.
+    >>> Triangle(1, 2, 3)
+    Traceback (most recent call last):
+        ...
+    ValueError: side lengths do not form a valid triangle.
+    """
+
+    def __init__(self, side_a_length: float, side_b_length: float, side_c_length: float) -> None:
+        super().__init__()
+        self.side_a_length = side_a_length
+        self.side_b_length = side_b_length
+        self.side_c_length = side_c_length
+        self.post_init()
+
+    def post_init(self) -> None:
+        self.side_a = Side(self.side_a_length)
+        self.side_b = Side(self.side_b_length)
+        self.side_c = Side(self.side_c_length)
+
+        if not self._is_valid_triangle(self.side_a.length, self.side_b.length, self.side_c.length):
+            raise ValueError("side lengths do not form a valid triangle.")
+
+        super().add_side(self.side_a)
+        super().add_side(self.side_b)
+        super().add_side(self.side_c)
+
+    @staticmethod
+    def _is_valid_triangle(a: float, b: float, c: float) -> bool:
+        return a + b > c and a + c > b and b + c > a
+
+    def perimeter(self) -> float:
+        return self.side_a.length + self.side_b.length + self.side_c.length
+
+    def area(self) -> float:
+        s = self.perimeter() * 0.5
+        return math.sqrt(s * (s - self.side_a.length) * (s - self.side_b.length) * (s - self.side_c.length))
+
+
 if __name__ == "__main__":
     __import__("doctest").testmod()

From f12f06588a8a929a8c7d5822929b4657e55e69f3 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Thu, 18 Sep 2025 21:29:07 +0000
Subject: [PATCH 2/2] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 geometry/geometry.py | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/geometry/geometry.py b/geometry/geometry.py
index 2c7ee0f1f556..390111df69d4 100644
--- a/geometry/geometry.py
+++ b/geometry/geometry.py
@@ -303,7 +303,9 @@ class Triangle(Polygon):
     ValueError: side lengths do not form a valid triangle.
     """
 
-    def __init__(self, side_a_length: float, side_b_length: float, side_c_length: float) -> None:
+    def __init__(
+        self, side_a_length: float, side_b_length: float, side_c_length: float
+    ) -> None:
         super().__init__()
         self.side_a_length = side_a_length
         self.side_b_length = side_b_length
@@ -315,7 +317,9 @@ def post_init(self) -> None:
         self.side_b = Side(self.side_b_length)
         self.side_c = Side(self.side_c_length)
 
-        if not self._is_valid_triangle(self.side_a.length, self.side_b.length, self.side_c.length):
+        if not self._is_valid_triangle(
+            self.side_a.length, self.side_b.length, self.side_c.length
+        ):
             raise ValueError("side lengths do not form a valid triangle.")
 
         super().add_side(self.side_a)
@@ -331,7 +335,12 @@ def perimeter(self) -> float:
 
     def area(self) -> float:
         s = self.perimeter() * 0.5
-        return math.sqrt(s * (s - self.side_a.length) * (s - self.side_b.length) * (s - self.side_c.length))
+        return math.sqrt(
+            s
+            * (s - self.side_a.length)
+            * (s - self.side_b.length)
+            * (s - self.side_c.length)
+        )
 
 
 if __name__ == "__main__":