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There are methods to add two lines of arbitrary lengths or multiply them together known since Greek times; and more advanced methods based on the concepts of bases and units.

But, I have not been able to find a way to exponentiate a number geometrically without using algebra. I would love if someone could somehow illustrate the concept.

Basically I am asking is it possible to draw the graph of a^x geometrically.

On questions raised by Aretino and RickyDemer I want to clarify that: I am talking about Euclidean geometry (so a collapsible compass,straight-edge are allowed); although, Cartesian geometry is fine, too.

Also, is there a book that can teach a basic concept as this? You know, a book on Euclidean geometry that teaches exponentiation, multiplication etc.

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  • $\begingroup$ For integer exponents, you could consider $a^n$ as the volume of an $n$-dimensional cube with side lengths of $a$ $\endgroup$
    – Christian
    Commented Aug 28, 2016 at 16:29
  • $\begingroup$ @Christian What about fractional exponents? And, how exactly can I illustrate the concept on n-dimensional cube in Euclidean geometry? $\endgroup$
    – Abdur Rahman
    Commented Aug 28, 2016 at 16:32
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    $\begingroup$ do you mean to construct a number $a^n$ from a given segment of length $a$ and $1$? $\endgroup$
    – user345851
    Commented Aug 28, 2016 at 16:33
  • $\begingroup$ en.wikipedia.org/wiki/Doubling_the_cube ​ ​ $\endgroup$
    – user57159
    Commented Aug 28, 2016 at 16:35
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    $\begingroup$ He's talking about the theorem on the page my initial comment linked to. ​ ​ $\endgroup$
    – user57159
    Commented Aug 28, 2016 at 16:57

1 Answer 1

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Let $AB = 1$, $AD=a$. We draw another line at any angle with $AB$, mark a point C on it such that $AC=a$. Let a line through $D$ parallel to $BC$ meet this line at $E$enter image description here, then $AE=a^2$, continuing this way we can raise it to any integer power.

Using this you can only calculate negative integral powers as well. Calculation of square roots is simple so we can construct all numbers of form $a^\frac{n}{2}$. But we cannot go cube roots or anything as using scale and compass we are limited to square roots.

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    $\begingroup$ Does it also work for fractional or negative powers? Also, could you provide a source where I could get a wee bit more insight. Thank you. $\endgroup$
    – Abdur Rahman
    Commented Aug 28, 2016 at 16:46

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