(a)
Compute the sums of the squares of Rows 1-4 of Pascal's Triangle.
Central binomial coefficients: \(\dbinom{2n}{n}\)
see: http://oeis.org/search?q=1%2C2%2C6%2C20%2C70&sort=&language=english&go=Suche
\(\begin{array}{|rcll|} \hline \large{\sum \limits_{k=0}^{n} \dbinom{n}{k}^2 = \dbinom{2n}{n} }\\ \hline \end{array}\)
Because the exterior angle of an octagon is 45°, we can extend | |
sides BA and GH to point J to create 45-45-90 triangle AJH | |
In △AJH, | |
the side across from the 90° angle = AH = 2 |
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the sides across from the 45° angles = AJ = JH = 2 / √2 = √2 | |
By the Pythagorean Theorem, |
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AG2 = AJ2 + JG2 |
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AG2 = AJ2 + (JH + HG)2 |
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AG2 = (√2)2 + (√2 + 2)2 |
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AG2 = 2 + 2 + 4√2 + 4 |
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AG2 = 8 + 4√2 |
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AG2 ≈ 13.657 |
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That is in square cm. |
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