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(a) Look at figure 23. There are four paths from the point B. One leads to A; where do the others lead?
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(b) How many paths are there from C?
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(c) State the order of each node marked with a letter in figure 23.
EXERCISE B
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1. Make a list of the letters which have among
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others: NOTE: PROVIDE EACH STUDENT A COPY of 26
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LETTERS.
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(a) One 3node, (b) two 3nodes, (c) one 4node.
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2. Why is it impossible to draw a figure with one 1node and no other nodes?
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3. Which of the letters in question 1 are topological transformations of the letter C?
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4. Which of the letters in question 1 are equivalent to the letter Y? How many nodes has each of these letters? What kind of nodes are they? NOTE: WE DO NOT COUNT 2NODES SINCE EVERY POINT OF AN ARC IS 2NODE WITH THE EXCEPTION OF ITS ENDS.
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5. Complete the table for the networks in figure 24. NOTE: PROVIDE EACH STUDENT A COPY OF FIGURE 24 AND ADD 5 MORE DIAGRAMS.
INVESTIGATION 1
Draw, if possible, figures which have:
NETWORK
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1NODE
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3NODES
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4NODES
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5NODES
|
6NODES
|
1.
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—
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—
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2
|
—
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—
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2.
|
—
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4
|
1
|
—
|
—
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3.
|
—
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—
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—
|
—
|
1
|
4.
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4
|
—
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1
|
—
|
—
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5.
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1
|
1
|
—
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—
|
—
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6.
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—
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1
|
1
|
1
|
—
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7.
|
—
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3
|
—
|
—
|
—
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8.
|
—
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2
|
1
|
—
|
—
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(a) Make up some more examples of your own.
(b) When is it impossible to draw a figure?
(c) Try to find a rule for deciding whether or not a figure can be drawn.