Let
α = m → ∞ lim n → ∞ lim [ cos ( n ! π x ) ] 2 m
When x is rational
β = m → ∞ lim n → ∞ lim [ c o s ( n ! π x ) ] 2 m
When x is irrational
Then the area of the triangle formed by vertices ( α , β ) , ( π e , − π ), ( e π , e ) is A
Then find 'A + 3'
Also try Crazy Limits!!! 1
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Are you implying that they cheated?
i inserted 66, thinking you wanted the floor ;; _ _;;;
Thanks. Given the edits to your question, those who previously answered 63, 64, 66 have been marked correct. The correct answer is now 67.
An additional comment: Note that when x is rational, we can always take n large enough so that the argument of cos is an even multiple of π , thus leading to the limit lim n → ∞ cos ( n ! π x ) = 1 . Similarly, when x is irrational, no matter how large n is n ! x can never be of the form k π , leading to values of cos ( n ! π x ) lying in the range − 1 , 1 ,. So, the use of 2 m is actually not needed here and the same answer can be obtained if 2 m is replaced by m .
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First of all we will solve α
Now
Let x = q p
Substituting in α
α = m → ∞ lim n → ∞ lim [ c o s ( n ! π q p ) ] 2 m
Now we observer that
q will cancel out 100% (with one term of n!)
Then we will get
Cos as multiple of π
And we know that
c o s ( n π ) = ± 1
But the power is 2m, taking 2 inside we will only get
c o s ( w h a t e v e r ) = 1
And 1 ∞ = 1
We finally get
α = 1
Now solving for β
As x is irrational let is be x
β = m → ∞ lim n → ∞ lim [ c o s ( n ! π x ) ] 2 m
Now
Cos(whatever) will oscillate b/w ± 1
As the power is 2m, taking 2 inside
Cos(whatever) will oscillate b/w
0 and 1
Let angle of cos be 'k'
m → ∞ lim [ c o s ( k ) ] m = 0
Hence we get
α = 1 , β = 0
Finding the area will require calculator which you can do (comes around 63.94)
Final answer comes 67