60 / 200 : narrow random rotation angle to avoid degenerate cases

`nr.randint(-180, 180)` could land on near-zero or near-±180° angles,
producing rotations close to identity or to a 180° flip. In both cases
the power-iteration example becomes ambiguous (no clearly dominant
eigendirection over a single rotation). Replace with a random choice
from `[-170, -10] ∪ [10, 170]` and import `random` accordingly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Clean ipynb 62019ec

Author: kwlee2025cpp

60_linear_algebra_2/200_Eigenvalues_of_a_Matrix_PowerMethod.ipynb

@@ -626,7 +626,18 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "theta_rad = np.deg2rad(nr.randint(-180, 180))\n",
+    "import random\n",
+    "\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "deg_list = list(range(-170, -10)) + list(range(10, 170+1))\n",
+    "theta_rad = np.deg2rad(random.choice(deg_list))\n",
     "\n",
     "matA = np.array(\n",
     "    [\n",
@@ -727,8 +738,8 @@
  ],
  "metadata": {
   "colab": {
-   "provenance": [],
-   "include_colab_link": true
+   "include_colab_link": true,
+   "provenance": []
   },
   "kernelspec": {
    "display_name": "Python 3 (ipykernel)",
@@ -745,9 +756,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.9"
+   "version": "3.13.12"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 0
+ "nbformat_minor": 4
 }