diff --git a/CHANGELOG.md b/CHANGELOG.md
index 32a6aca..fdd6b34 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,14 @@
 
 모든 중요한 변경 사항은 이 문서에 기록됩니다. 형식은 [Keep a Changelog](https://keepachangelog.com/ko/1.1.0/)과 [Semantic Versioning](https://semver.org/lang/ko/)을 따릅니다.
 
+## [Unreleased]
+
+### 고침
+
+- EqEdit의 공식 `TRIANGLE` 토큰과 실문서에서 관측된 소문자 `triangle` 토큰을
+  `\triangle`로 변환한다. 미리보기 MathML에서도 삼각형을 식별자 문자열이 아닌
+  수학 연산자 기호로 보존하며, 혼합 대소문자나 더 긴 식별자는 해석하지 않는다.
+
 ## [6.3.0] - 2026-08-19
 
 ### 더함
diff --git a/src/hwpx/equation/mathml.py b/src/hwpx/equation/mathml.py
index 097a2ff..97ce5c0 100644
--- a/src/hwpx/equation/mathml.py
+++ b/src/hwpx/equation/mathml.py
@@ -9,11 +9,15 @@
 
 from __future__ import annotations
 
+import re
 from typing import Callable
 
+from .tokens import EQEDIT_MATHML_OPERATOR_COMMANDS
+
 # ``False`` marks a resolved-but-unavailable converter; ``None`` means "not yet
 # probed" so the import is attempted lazily on first use.
 _converter: Callable[[str], str] | bool | None = None
+_LATEX_WORD_COMMAND_RE = re.compile(r"\\[A-Za-z]+")
 
 
 class MathMLUnavailableError(RuntimeError):
@@ -62,8 +66,27 @@ def latex_to_mathml(latex: str) -> str:
         raise ValueError(f"latex2mathml could not render fragment: {exc}") from exc
 
 
+def eqedit_latex_to_mathml(latex: str) -> str:
+    """Convert EqEdit-derived LaTeX while preserving known token roles.
+
+    ``latex2mathml`` classifies plain ``\\triangle`` as an identifier. EqEdit's
+    token map identifies it as a mathematical symbol, so the MathML-only input
+    receives an operator wrapper before conversion. The returned/public LaTeX
+    is not rewritten, and serialized MathML is never patched afterward.
+    """
+
+    def annotate_role(match: re.Match[str]) -> str:
+        command = match.group(0)
+        if command in EQEDIT_MATHML_OPERATOR_COMMANDS:
+            return rf"\mathop{{{command}}}"
+        return command
+
+    return latex_to_mathml(_LATEX_WORD_COMMAND_RE.sub(annotate_role, latex))
+
+
 __all__ = [
     "MathMLUnavailableError",
+    "eqedit_latex_to_mathml",
     "latex2mathml_available",
     "latex_to_mathml",
 ]
diff --git a/src/hwpx/equation/render.py b/src/hwpx/equation/render.py
index 33b53e8..8710da7 100644
--- a/src/hwpx/equation/render.py
+++ b/src/hwpx/equation/render.py
@@ -18,7 +18,7 @@
 import html
 
 from .eqedit import EquationConversionError, eqedit_to_latex
-from .mathml import MathMLUnavailableError, latex_to_mathml
+from .mathml import MathMLUnavailableError, eqedit_latex_to_mathml
 
 # Fidelity labels surfaced in the preview (Constitution IX, honest reporting).
 LABEL_MATHML = "수식 MathML 렌더"
@@ -63,7 +63,7 @@ def render_equation(script: str) -> EquationRender:
         return _fallback_block("script", LABEL_SCRIPT, script, latex=None)
 
     try:
-        mathml = latex_to_mathml(latex)
+        mathml = eqedit_latex_to_mathml(latex)
     except MathMLUnavailableError:
         return _fallback_block("latex", LABEL_LATEX_NO_LIB, latex, latex=latex)
     except ValueError:
diff --git a/src/hwpx/equation/tokens.py b/src/hwpx/equation/tokens.py
index 5a08030..d6f6066 100644
--- a/src/hwpx/equation/tokens.py
+++ b/src/hwpx/equation/tokens.py
@@ -116,6 +116,11 @@
     "partial": r"\partial",
     "nabla": r"\nabla",
     "angle": r"\angle",
+    # Hancom's symbol guide spells this token in uppercase, while legacy
+    # documents also contain the exact lowercase form. Mixed-case variants are
+    # intentionally not accepted because the reader uses exact token lookup.
+    "triangle": r"\triangle",
+    "TRIANGLE": r"\triangle",
     "cdots": r"\cdots",
     "ldots": r"\ldots",
     "vdots": r"\vdots",
@@ -254,11 +259,17 @@
 # Structural keywords handled directly by the parser (not simple substitution).
 STRUCTURAL = frozenset({"over", "atop", "sqrt", "root", "of", "LEFT", "RIGHT", "left", "right"})
 
+# LaTeX commands emitted from EqEdit operator tokens that latex2mathml otherwise
+# classifies as identifiers. The render boundary uses this metadata only while
+# producing MathML; the public LaTeX remains the canonical command above.
+EQEDIT_MATHML_OPERATOR_COMMANDS = frozenset({OPERATORS["triangle"]})
+
 
 __all__ = [
     "ACCENTS",
     "BIG_OPERATORS",
     "DELIMITERS",
+    "EQEDIT_MATHML_OPERATOR_COMMANDS",
     "FUNCTIONS",
     "GREEK",
     "MATRIX_ENVIRONMENTS",
diff --git a/tests/test_equation_authoring.py b/tests/test_equation_authoring.py
index 22ba251..87a6c82 100644
--- a/tests/test_equation_authoring.py
+++ b/tests/test_equation_authoring.py
@@ -222,6 +222,7 @@ class TestLatexToEqedit:
             (r"$x + 1$", "x + 1"),
             (r"\le \ge \ne", "leq geq neq"),
             (r"a \times b \cdot c \div d", "a times b cdot c div d"),
+            (r"\triangle P_1 P_2 Q", "triangle P _{1} P _{2} Q"),
             (r"\lim_{x \to 0} \frac{1}{x}", "lim _{x -> 0} {1} over {x}"),
             (r"a \to b", "a -> b"),
             (r"x \rightarrow y , u \leftarrow v", "x -> y , u leftarrow v"),
@@ -274,6 +275,7 @@ class TestRoundtripStability:
         r"\begin{vmatrix} a & b \\ c & d \end{vmatrix}",
         r"\log_{2} x + \ln y",
         r"a \times b \pm c \mp d",
+        r"\triangle P_1 P_2 Q",
         r"\infty + \partial + \nabla",
     ]
 
diff --git a/tests/test_equation_converter.py b/tests/test_equation_converter.py
index b471387..89b052d 100644
--- a/tests/test_equation_converter.py
+++ b/tests/test_equation_converter.py
@@ -112,6 +112,31 @@ def test_times_and_relations() -> None:
     assert eqedit_to_latex("a >= b") == r"a \geq b"
 
 
+@pytest.mark.parametrize("token", ["triangle", "TRIANGLE"])
+def test_triangle_symbol_uses_exact_evidence_backed_tokens(token: str) -> None:
+    assert eqedit_to_latex(f"{token} P_1 P_2 Q") == r"\triangle P_1 P_2 Q"
+
+
+@pytest.mark.parametrize(
+    "script",
+    [
+        "Triangle PQR",
+        "triAngle PQR",
+        "triangles PQR",
+        "mytriangle PQR",
+        "triangleidentifier PQR",
+        "rmtriangle PQR",
+        "rm text",
+    ],
+)
+def test_triangle_support_does_not_split_identifiers_or_rm_text(script: str) -> None:
+    assert eqedit_to_latex(script) == script
+
+
+def test_existing_angle_symbol_remains_distinct_from_triangle() -> None:
+    assert eqedit_to_latex("angle ABC") == r"\angle ABC"
+
+
 def test_parentheses_and_braces_passthrough() -> None:
     assert eqedit_to_latex("( a + b )") == "( a + b )"
     assert eqedit_to_latex("LEFT ( x RIGHT )") == r"\left( x \right)"
diff --git a/tests/test_equation_render.py b/tests/test_equation_render.py
index c8b1973..07d9bc6 100644
--- a/tests/test_equation_render.py
+++ b/tests/test_equation_render.py
@@ -3,6 +3,8 @@
 
 from __future__ import annotations
 
+from xml.etree import ElementTree
+
 import pytest
 
 from hwpx.equation import (
@@ -25,6 +27,23 @@ def test_success_path_renders_inline_mathml() -> None:
     assert result.latex == r"\frac{\alpha}{\beta} + \pi"
 
 
+@pytest.mark.parametrize("token", ["triangle", "TRIANGLE"])
+def test_triangle_renders_as_mathml_operator_without_changing_latex(token: str) -> None:
+    pytest.importorskip("latex2mathml")
+    result = render_equation(f"{token} P_1 P_2 Q")
+    assert result.mode == "mathml"
+    assert result.latex == r"\triangle P_1 P_2 Q"
+    root = ElementTree.fromstring(result.html)
+    namespace = "{http://www.w3.org/1998/Math/MathML}"
+    triangle_operators = [
+        operator
+        for operator in root.iter(f"{namespace}mo")
+        if "△" in "".join(operator.itertext())
+    ]
+    assert len(triangle_operators) == 1
+    assert "triangle" not in "".join(root.itertext()).lower()
+
+
 def test_eqedit_failure_falls_back_to_original_script_block() -> None:
     # A brace/frac bomb exceeds the depth guard -> EqEdit->LaTeX fails.
     bomb = "{" * 200 + "x" + "}" * 200