Can YOU find the length with only one measure?

Geometry Level 1

Consider the above diagram, with:

  • A E = A D AE=AD
  • Square B C D E BCDE , with a circle circumscribed.
  • C D = 2 2 CD=2\sqrt{2}
  • B E A E \frac{BE}{AE} can be written as a b + ( c d ) k \frac{\sqrt{a}}{\sqrt{b+(c-\sqrt{d}) ^ k}} , where every variable is equal to a natural number under 10.
  • y = k a ( d b ) c ) y=k ^ a-(d ^ b)^c)
  • y a \frac{y}{a} can be written as f g \frac{f}{g} , where g c f ( g , f ) = 1 gcf(g, f)=1
  • f g = x f-g=x

What is the value of x x ?


The answer is 29.

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1 solution

Robert Haywood
Nov 27, 2014

B E = 2 2 BE=2\sqrt{2} , since all sides of a square are equal: C D = B E = 2 2 CD=BE=2\sqrt{2} . Easy. Now, to find AE:

The diameter of this circle is also equal to one of square's diagonals. The length of the diagonal of a square is equal to s 2 s\sqrt{2} , where s s is a side length. In this case, s = 2 2 s=2\sqrt{2} , so we get 2 2 2 = 2 2 = 4 2\sqrt{2}*\sqrt{2}=2*2=4 . So, if d d is the diameter, d = 4 d=4 . The radius, r r , is equal to d 2 \frac{d}{2} , which means that r = 4 2 = 2 1 = 2 r=\frac{4}{2}=\frac{2}{1}=2 . Take the center of the circle (and the square as well), and call it Point F. F E = 2 FE=2 , since that would be half of a diagonal. A F = r = 2 AF=r=2 , and Point G is the point of intersection of A F AF and E D ED . If we were to find the length of A G AG , we could create a right triangle with vertices A,G, and E, with A E AE as the hypotenuse! A G = r G F AG=r-GF . Since it is half of a side (this should be easy to visualize), G F = 2 2 2 = 2 GF=\frac{2\sqrt{2}}{2}=\sqrt{2} . Therefore, A G = 2 2 AG=2-\sqrt{2} . Leave that there. Now, E G = G F EG=GF since they are both halves of sides, so E G = 2 EG=\sqrt{2} . Now, we can use the Pythagorean Theorem to solve for A E AE ! 2 2 + ( 2 2 ) 2 = A E \sqrt{2} ^ 2+(2-\sqrt{2}) ^ 2=AE . If we were to plug this into the variables in the denominator of the problem, we find that it fits perfectly! For B E BE , 2 2 = 8 2\sqrt{2}=\sqrt{8} , so:

  • a = 8 a=8
  • b = 2 b=2
  • c = 2 c=2
  • d = 2 d=2
  • k = 2 k=2

Plugging these variables into the equation for y, we get

y = 2 8 ( 2 2 ) 2 = 256 4 2 = 256 16 = 240 y=2^8-(2^2)^2=256-4^2=256-16=240

Plugging our new value into the next equation, we find

240 8 = 30 1 \frac{240}{8}=\frac{30}{1}

Since the GCF of the numbers in that second fraction is 1, that means that

  • f = 30 f=30
  • g = 1 g=1

Plug THESE into the last equation:

x = 30 1 = 29 x=30-1=29

Therefore, our answer is 29 \boxed{29} !

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