Update Readme.md

journal/Readme.md

 # Part 1： Writing a Markdown file
 
 
-# Part 2：Exercice 02
+# Part 2： Exercice 02
 ## 2.1 Using a notebook
 ### 2.1.1  About Calculating π
 My computer tells me that π is approximately **3.141592653589793**
 
 ### 2.1.2  Using Buffon's Needle Method
-But calculated using the [Buffon's needle](https://en.wikipedia.org/wiki/Buffon's_needle) method, we would obtain as an approximation **3.128911138923655**
+But calculated using the [Buffon's needle](https://en.wikipedia.org/wiki/Buffon's_needle) method, we would obtain as an approximation **3.128911138923655**
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+
+### 2.1.3  With a "Surface Frequency" Argument
+Otherwise, by applying a Monte Carlo method to a quarter-circle surface of radius 1, we approach $\pi$/4
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