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Proof Question - AS

Prove that the distance between two opposite edges of a regular hexagon of side length root 3 is a rational value.

Can someone please explain why they have used pythagoras and what led them to use it? I don't understand the mark scheme. I assumed maybe sine/ cosine rule would be involved as 120 degrees is the angle in a regular hexagon.
(edited 4 years ago)
Reply 1
Original post by Sidd1
Prove that the distance between two opposite edges of a regular hexagon of side length root 3 is a rational value.

Can someone please explain why they have used pythagoras and what led them to use it? I don't understand the mark scheme. I assumed maybe sine/ cosine rule would be involved as 120 degrees is the angle in a regular hexagon.


That answer is wrong. Have you sketched it?
you could use Pythagoras or the Cosine Rule.
Reply 3
Original post by mqb2766
That answer is wrong. Have you sketched it?

How do you know it's wrong? Yeah I have I'll upload it now:smile:proof question AS .jpg
Reply 4
Original post by Sidd1
How do you know it's wrong? Yeah I have I'll upload it now:smile:proof question AS .jpg


The hexagon is made from 6 identical equllateral triangles of side length sqrt(3). The center is where the vertices coincide. Can you add this?
Reply 5
if you split the one of the equilateral triangles into two isosceles triangles, you have angles 90 degrees - right angle, 60 degrees - 120 degrees / 2, and 30 degrees - 180-90-60. Since we split each equilateral triangle into two isosceles, the length of one of the sides is root 3 / 2. From there, we can use the sin rule. x / sin60 = root 3 / 2 / sin30. rearrange for x (x = sin60 x root 3 / 2 / sin30) and you get an answer of 3/2.
Reply 6

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