Help with a Mathematical Induction Problem

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The discussion focuses on proving the inequality 1/2 * 3/4 ... 2n-1/2n < 1/sqrt(3n) using mathematical induction. The basis step is confirmed to work for n=1, but the inductive step fails when trying to show the inequality holds for n+1. The failure is demonstrated by comparing the values for n=1, where the left side is approximately 0.43 and the right side is approximately 0.40. However, the discussion indicates that the stronger inequality 1/2 * 3/4 ... 2n-1/2n < 1/sqrt(3n+1) can be proven successfully using mathematical induction. This highlights the importance of verifying both the basis and inductive steps in mathematical proofs.
Walshy1
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Suppose we want to prove that: 1/2 * 3/4 ... 2n-1/2n < 1/sqrt(3n)

for all positive integers.
(a) Show that if we try to prove this inequality using mathematical induction, the basis step works, but
the inductive step fails.(b) Show that mathematical induction can be used to prove the stronger inequality: 1/2 * 3/4 ... 2n-1/2n < 1/sqrt(3n+1)

So far I have proven the basis step works in part a by plugging in 1, however, I do not know how to say the inductive step fails. I have no clue on part b. Thanks.
 
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The inductive step would require you to show that

$$\frac{1}{2} \cdot \frac{3}{4} \cdots \frac{2n-1}{2n} \cdot \frac{2n+1}{2(n+1)} < \frac{1}{\sqrt{3(n+1)}}.$$

Following the inductive step, we know that

$$\frac{1}{2} \cdot \frac{3}{4} \cdots \frac{2n-1}{2n} < \frac{1}{\sqrt{3n}},$$

therefore we can conclude that

$$\frac{1}{2} \cdot \frac{3}{4} \cdots \frac{2n-1}{2n} \cdot \frac{2n+1}{2(n+1)} < \frac{1}{\sqrt{3n}} \cdot \frac{2n+1}{2(n+1)}.$$

Now do a simple test: take $n=1$. Our expression yields $\approx 0.43$, whereas the proposed one generates $\approx 0.40$. Our inductive step fails! :p

You should proceed the same way for the next item, bearing in mind that now the inequality will be true. ;)
 
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