assignment 25

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course mth 152

12/19/1310:58am

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Question: `q Query 9.7.6 intersecting lines m, n parallel to k **** In which geometry or geometries is this possible and why?

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Your solution:

Two parallel lines intersect on a sphere

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Given Solution:

** Two parallel lines intersect on a sphere (think of lines of longitude). So this occurs in a Riemannian geometry. **

STUDENT COMMENT

OK, not so sure how they intersect even on a sphere. I see they will connect with themselves, but not how the parallel

intersect.

INSTRUCTOR RESPONSE

If you start here and go due north, while I start 100 miles to the west and go due north, then we are moving in parallel directions.

If we both continue moving due north, we will always be moving parallel, and we will meet at the north pole.

The Earth isn't quite a perfect sphere, so this isn't literally true, but it would be as described on a perfect sphere.

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Question: `q Query 9.7.18 ruler r.b. CD wrench nail **** To which of the objects is the coin topologically equivalent and why?

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Your solution:

The coin is topologically equivalent to the ruler and the nail neither of these have holes.

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Given Solution:

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Question: `q Query 9.7.27 genus of 3-hole-punched sheet of paper **** What is the genus of the sheet and why?

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Your solution:

its 3 because it has 3 holes

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Given Solution:

`a The genus of this sheet of paper is 3 becasue it contains 3 holes.

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Question: `q Query 9.7.42 3,3,3,3,4,4,2,2 **** Can the network be traversed or not and why?

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Your solution:

contains 4 odd vertices. A network with 0 or 2 odd vertices can be traversed; 4 odd vertices cannot

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Given Solution:

`a ** This network contains 4 odd vertices. A network with 0 or 2 odd vertices can be traversed; a network with 4 odd vertices cannot. **

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Question: `q **** If you start on a vertex of order 3 can you traverse the network and end up on that vertex? Explain why your answer must be true.

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Your solution:

contains 4 odd vertices. A network with 0 or 2 odd vertices can be traversed; a network with 4 odd vertices cannot

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Given Solution:

This network contains 4 odd vertices. A network with 0 or 2 odd vertices can be traversed; a network with 4 odd vertices cannot.

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Question: `q **** If you start on a vertex of order 4 can you traverse the network and end up not on that vertex? Explain why your answer must be true.

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Your solution:

4 you cannot traverse the network without ending up on that vertex, the second one ends on the third

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Given Solution:

`a ** If you start on a vertex of order 4 you cannot traverse the network without ending up on that vertex, since you leave the vertex on the first edge, return on the second and leave on the third. If you traverse the network you have to return to the vertex on the fourth edge, and you can’t leave again. **

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Question: `q **** If you start on a vertex of order 2 and traverse the network must you end up on that vertex? Explain why your answer must be true.

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Your solution: If you start on a vertex of order 2 and traverse the network you leave on the first edge, return on the 2 nd

No, because this is an even vertex.

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Given Solution:

`a ** If you start on a vertex of order 2 and traverse the network you leave on the first edge, return on the 2 nd and you’re stuck there. **

No, because once again this is an even vertex. One point must be the starting point and one the ending point.

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Question: `q **** If you start off of a certain vertex of order 3 and traverse the network is it possible to end up somewhere besides this vertex?

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Your solution:

3 and traverse the network you leave on the first, return on the second and leave on the third edge you must end up elsewhere

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Given Solution:

`a ** If you start on a vertex of order 3 and traverse the network you leave on the first, return on the second and leave on the third edge. You can’t travel any of these edges again so you can never return. Therefore you must end up elsewhere. **

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Question: `q Query Add comments on any surprises or insights you experienced as a result of this assignment.

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Question: `q Query Add comments on any surprises or insights you experienced as a result of this assignment.

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&#Good responses. Let me know if you have questions. &#