diff --git a/app/layout.tsx b/app/layout.tsx
index 5b452ed..c8870eb 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -5,6 +5,7 @@ import { getPageMap } from 'nextra/page-map'
 import 'nextra-theme-docs/style.css'
 import { SpeedInsights } from "@vercel/speed-insights/next"
 import { Analytics } from "@vercel/analytics/react"
+import 'katex/dist/katex.min.css'
 
 export const metadata = {
   metadataBase: new URL('https://notenextra.trance-0.com'),
diff --git a/content/Math401/Math401_P1_2.md b/content/Math401/Math401_P1_2.md
index fddb5cd..6765a34 100644
--- a/content/Math401/Math401_P1_2.md
+++ b/content/Math401/Math401_P1_2.md
@@ -4,8 +4,29 @@ The page's lemma is a fundamental result in quantum information theory that prov
 
 ## Statement
 
-Let $\mathcal{H}$ be a Hilbert space and $\mathcal{L}(\mathcal{H})$ be the set of linear operators on $\mathcal{H}$.
+Choosing a random pure quantum state $\rho$ from the bi-partite pure state space $\mathcal{H}_A\otimes\mathcal{H}_B$ with the uniform distribution, the expected entropy of the reduced state $\rho_A$ is:
 
-Let $\mathcal{E}: \mathcal{L}(\mathcal{H}) \to \mathcal{L}(\mathcal{H})$ be a quantum channel.
+$$
+\mathbb{E}[H(\rho_A)]\geq \ln d_A -\frac{1}{2\ln 2} \frac{d_A}{d_B}
+$$
 
-Then, for any $\rho \in \mathcal{L}(\mathcal{H})$, we have:
\ No newline at end of file
+## Page's conjecture
+
+A quantum system $AB$ with the Hilbert space dimension $mn$ in a pure state $\rho_{AB}$ has entropy $0$ but the entropy of the reduced state $\rho_A$, assume $m\leq n$, then entropy of the two subsystem $A$ and $B$ is greater than $0$.
+
+unless $A$ and $B$ are separable.
+
+In the original paper, the entropy of the average state taken under the unitary invariant Haar measure is:
+
+$$
+S_{m,n}=\sum_{k=n+1}^{mn}\frac{1}{k}-\frac{m-1}{2n}
+$$
+
+
+
+
+## References
+
+- [Page's conjecture](https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.71.1291)
+
+- [Page's conjecture simple proof](https://journals.aps.org/pre/pdf/10.1103/PhysRevE.52.5653)
\ No newline at end of file
diff --git a/next.config.mjs b/next.config.mjs
index 96bf57a..b3e5e44 100644
--- a/next.config.mjs
+++ b/next.config.mjs
@@ -2,7 +2,13 @@ import nextra from 'nextra'
 import withBundleAnalyzer from '@next/bundle-analyzer'
 
 const withNextra = nextra({
-  latex: true,
+  latex: {
+    renderer: 'katex',
+    options: {
+      // suppress warnings from katex for `\\`
+      strict: false,
+    }
+  },
   mdxOptions: {
     format: 'detect'
   },
diff --git a/package-lock.json b/package-lock.json
index bbb53e0..a04b488 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -9,6 +9,7 @@
         "@vercel/analytics": "^1.5.0",
         "@vercel/speed-insights": "^1.2.0",
         "cross-env": "^7.0.3",
+        "katex": "^0.16.22",
         "next": "^15.3.5",
         "next-sitemap": "^4.2.3",
         "nextra": "^4.2.17",
diff --git a/package.json b/package.json
index 8f0fe3a..5d82549 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
     "@vercel/analytics": "^1.5.0",
     "@vercel/speed-insights": "^1.2.0",
     "cross-env": "^7.0.3",
+    "katex": "^0.16.22",
     "next": "^15.3.5",
     "next-sitemap": "^4.2.3",
     "nextra": "^4.2.17",