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Given the following text description, write Python code to implement the functionality described.
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Description:
Largest rectangle that can be inscribed in a semicircle
Function to find the area of the biggest rectangle ; the radius cannot be negative ; area of the rectangle ; Driver Code

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Python Code:
def rectanglearea(r ) : 
	 if r < 0 : 
	 return - 1 
  a = r * r 
 return a 
  if __name__== "__main __": 
	 r = 5 
 
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