This is my method to check if a given number is in the Fibonacci sequence by using the equation in the 'recognizing fibonacci numbers' section of this wikipedia page: http://en.wikipedia.org/wiki/Fibonacci_number#Recognizing_Fibonacci_numbers. I get that this can't handle large numbers as Float isn't precise enough at a certain point. Through my…

gistfile1.txt

def is_fibonacci?(i)
  fib1 = Math.sqrt((5*(i**2)+4))
  fib2 = Math.sqrt((5*(i**2)-4))
  puts fib1 == fib1.floor || fib2 == fib2.floor ? true : false
end

def is_fibonacci?(i)
fibs = [0,1]

while fibs.last < i
x = fibs.pop
y = fibs.pop
z = x + y
fibs << x
fibs << z
end
fibs.last == i ? true : false
end