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# how do you work this out? watch

1. how do you work part a and b out? I've thought all the interior angels are the same

2. (Original post by Wildnatxox)
how do you work part a and b out? I've thought all the interior angels are the same
Part (a) is right.

For part (b), the obvious triangle is isosceles so use its angle fact.
3. Regular means all sides are equal right? Then the part you're looking at is an isosceles triangle and you've already worked out the first part, use that answer to find y and you're good to go
4. (Original post by RDKGames)
Part (a) is right.

For part (b), the obvious triangle is isosceles so use its angle fact.
180 - 108?
5. y = (180 - x)/2
y = (180 - x)/2
how
7. (Original post by Wildnatxox)
180 - 108?
That would give the sum of the two other angles in the triangle. In an isosceles triangle, those angles are the same. So divide by 2 to get one of them, which is what is.
8. (Original post by RDKGames)
That would give the sum of the two other angles in the triangle. In an isosceles triangle, those angles are the same. So divide by 2 to get one of them, which is what is.

it looks like a scalene triangle
9. Angle Y and the opposite are the same, if you do 180(sum of the angles in a triangle) and subtract x you get the value for the angles y and the other, but both are the same so divide by 2 to get y
10. (Original post by Wildnatxox)
it looks like a scalene triangle
Not really... a scalene triangle is one where all of its sides are different lengths, here it looks like two sides are the same length.

Besides, it doesn't matter 'what it looks like' because the fact remains that two of its sides are sides of a regular pentagon, and all sides of the regular pentagon are the same, therefore the two sides of the triangle are the same.

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