text: # Recursion
  
  ## Steps in drawing out the recursive call.
  
  How to write a method that calls itself. https://www.youtube.com/watch?v=MyzFdthuUcA – Dave Feinberg’s video series.
  
  1. Write “if”.
  There must be at least 2 cases:, a recursive case (where the method calls itself) and a base case (where the method does not).
  2. Handle the simplest case(s). “Base Case”
  Simplest = no recursive call needed (no further loop)
  3. Write the recursive call(s).
  On the next simpler input/state, it may help to store the recursive call
  4. Assume the recursive call works .
  Ask yourself: What does it do?
  Ask yourself: How does it help?
  
  ## Factorial
  
  ### Base Case
  
  If n! is defined as the product of all positive integers from 1 to n, then:
  1! = 1*1 = 1
  2! = 1*2 = 2
  3! = 1*2*3 = 6
  4! = 1*2*3*4 = 24
  
  n! = 1*2*3*…*(n-2)*(n-1)*n
  and so on.
  Logically, n! can also be expressed n*(n-1)! .
  
  Therefore, at n=1, using n! = n*(n-1)!
  1! = 1*0!
  which simplifies to 1 = 0!
  
  ### Java Recursive Factorial Method
  
  ```// precondition: n >= 0
  public static in fact(int n) {
  if (n=0) return 1;
  else return fact(n-1) * n;
  }
  
  ```
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