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Little explorations with HP calculators (no Prime)
03-27-2017, 06:30 PM
Post: #35
RE: Little explorations with the HP calculators
(03-27-2017 06:14 PM)pier4r Wrote:  
(03-27-2017 06:01 PM)Dieter Wrote:  Right, in the end you realize that both formulas are the same. ;-)

How? One should be from the Pythagoras' theorem, a^2+b^2=c^2 (where I use the two sides of the triangle to get the hypotenuse) the other is the composition of the area of the square, made up from 4 triangles and one inner square. To me they sound as different models for different measurements. Could you explain me why are those the same?

Just do the math. On the one hand, \( s^2 + (s + 2r)^2 = 1\) from Phythagorus' Theorem as you observed. And your other observation is that
\[ 4 \cdot \underbrace{\frac{1}{2} \cdot s \cdot (s+2r)}_{\text{area of }\Delta}
+ \underbrace{(2r)^2}_{\text{area of } \Box} = 1 \]
Simplify the left hand side:
4 \cdot \frac{1}{2} \cdot s \cdot (s+2r) + (2r)^2 & =
2s^2+4rs + 4r^2 \\
& = s^2 + s^2 + 4rs + 4r^2 \\
& = s^2 + (s+2r)^2
\end{align} \]
Hence, both formulas are the same.

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RE: Little explorations with the HP calculators - Han - 03-27-2017 06:30 PM

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