Merge pull request lydiahallie#760 from gustavoiha/master

docs: make question 3 explanation more comprehensive

Author: jakeherp

README.md

@@ -142,7 +142,7 @@ Note that the value of `diameter` is a regular function, whereas the value of `p
 
 With arrow functions, the `this` keyword refers to its current surrounding scope, unlike regular functions! This means that when we call `perimeter`, it doesn't refer to the shape object, but to its surrounding scope (window for example).
 
-There is no value `radius` on that object, which returns `NaN`.
+Since there is no value `radius` in the scope of the arrow function, `this.radius` returns `undefined` which, when multiplied by `2 * Math.PI`, results in `NaN`.
 
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