Is the information sufficient 8?

Geometry Level pending

You have a Hexagon, named EUNHA S . Also, you are given that:

  • m ( E U ) = m ( E S ) = 19 m\left(\overline{EU}\right) = m\left(\overline{ES}\right) = 19
  • m ( U N ) = m ( N H ) = 180 m\left(\overline{UN}\right) = m\left(\overline{NH}\right) = 180
  • m ( H A ) = m ( A S ) = 181 m\left(\overline{HA}\right) = m\left(\overline{AS}\right) = 181
  • m ( U E S ) = m ( U N H ) = m ( H A S ) = 12 0 m \left(\angle UES\right) = m\left(\angle UNH\right) = m\left(\angle HAS\right) = 120^{\circ} \cdot

If the value of ( m ( E A ) ) 2 \left( m \left(\overline{EA}\right) \right)^2 can be express as a + b c a + b\sqrt{c} where c c is a prime, what is the value of a + b + c ? \left\lfloor \sqrt{a + b + c} \right \rfloor \ ?

Clarification:

m ( A X ) m \left(\overline{AX}\right) means the length or measurement of line segment A X AX for example, while m ( R E S ) m \left(\angle RES\right) means the measurement of angle R E S RES \cdot


For more problems like this, try answering this set .


The answer is 190.

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2 solutions

Ahmad Saad
Jul 20, 2017

Christian Daang
Jul 21, 2017

The problem came from this.

Consider an equilateral triangle E N A ENA , with a point P P located inside that triangle such that, E P = 19 , P N = 180 , P A = 181 \overline{EP} = 19 \ , \ \overline{PN} = 180 \ , \ \overline{PA} = 181 \ \cdot

Now, reflect point P P with respect to line segment E N EN . Let's name the point of reflection U U \ \cdot

So, we can conclude that: E U = 19 , U N = 180 \overline{EU} = 19 \ , \ \overline{UN} = 180 \ \cdot


Next, reflect point P P again, this time respect to line segment E A EA . Let's name the point of reflection S S \ \cdot

Again, we can conclude that: E S = 19 , S A = 181 \overline{ES} = 19 \ , \ \overline{SA} = 181 \ \cdot


Lastly, reflect point P P with respect to line segment A N AN . Let's name the point of reflection H H \ \cdot

So, we can conclude that H N = 180 , H A = 181 \overline{HN} = 180 \ , \ \overline{HA} = 181 \ \cdot


It is left to the readers how m ( U E S ) = m ( U N H ) = m ( H A S ) = 12 0 m \left(\angle UES\right) = m\left(\angle UNH\right) = m\left(\angle HAS\right) = 120^{\circ} \cdot

Connecting the 6 points will give us the Hexagon, named EUNHA S .


As E U S \triangle EUS is isosceles, E U S = 3 0 \implies \angle EUS = 30^{\circ}

As U N H \triangle UNH is isosceles, N U H = 3 0 \implies \angle NUH = 30^{\circ}

As S U H \triangle SUH is right (right-angled at U U ), E U N = 3 0 + 3 0 + 9 0 = 15 0 \implies \angle EUN = 30^{\circ} + 30^{\circ} + 90^{\circ} = 150^{\circ} \ \cdot

As the quadrilateral E U N P EUNP is a kite, E P N = 15 0 \implies \angle EPN = 150^{\circ} \ \cdot

and therefore,

( m ( E A ) ) 2 = ( m ( E N ) ) 2 = 1 9 2 + 18 0 2 2 ( 19 ) ( 180 ) ( cos ( 15 0 ) ) = 32761 + 3420 3 = a + b c a = 32761 , b = 3420 , c = 3 a + b + c = 32761 + 3420 + 3 = 190 \left( m \left(\overline{EA}\right) \right)^2 = \left( m \left(\overline{EN}\right) \right)^2 = 19^2 + 180^2 - 2(19)(180)( \cos (150^{\circ})) = 32761 + 3420\sqrt{3} = a + b\sqrt{c} \\ \implies a = 32761 \ , \ b = 3420 \ , \ c = 3 \\ \implies \left\lfloor \sqrt{a + b + c} \right \rfloor = \left\lfloor \sqrt{32761 + 3420 + 3} \right \rfloor = \boxed{190}


This is what is it look like. :)

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