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# 2.1 Inductive Reasoning

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1. 2.1 Inductive Reasoning

2. Inductive reasoning is the process of observing data, recognizing patterns, and making generalizations based on those patterns. • Conjecture is a generalization based on inductive reasoning

3. An example of inductive reasoning • Suppose your history teacher likes to give “surprise” quizzes. • You notice that, for the first four chapters of the book, she gave a quiz the day after she covered the third lesson. • Based on the pattern in your observations, you might generalize that you will have a quiz after the third lesson of every chapter.

4. Inductive reasoning can be used to makea conjecture about a number sequence • Consider the sequence 10, 7, 9, 6, 8, 5, 7, . . . • Make a conjecture about the rule for generating the sequence. • Then find the next three terms.

5. Solution • Look at how the numbers change from term to term • The 1st term in the sequence is 10. You subtract 3 to get the 2nd term. • Then you add 2 to get the 3rd term. • You continue alternating between subtracting 3 and adding 2 to generate the remaining terms. • The next three terms are 4, 6, and 3.

6. Describing Number and Geometric Patterns • Objectives: • Use inductive reasoning in continuing patterns Vocabulary • Inductive reasoning: • make conclusions based on patterns you observe • Conjecture: • conclusion reached by inductive reasoning based on evidence • Geometric Pattern: • arrangement of geometric figures that repeat

7. Geometric Patterns • Arrangement of geometric figures that repeat • Use inductive reasoning and make conjecture as to the next figure in a pattern Use inductive reasoning to find the next two figures in the pattern. Use inductive reasoning to find the next two figures in the pattern.

8. Geometric Patterns Describe the figure that goes in the missing boxes. Describe the next three figures in the pattern below.

9. Numerical Sequences and Patterns Arithmetic Sequence Add a fixed number to the previous term Find the common difference between the previous & next term Example Find the next 3 terms in the arithmetic sequence. 2, 5, 8, 11, ___, ___, ___ 14 17 21 +3 +3 +3 +3 +3 +3 What is the common difference between the first and second term? Does the same difference hold for the next two terms?

10. Investigation: Shape Shifters • Page 98 • In the investigation you look at a pattern in a sequence of shapes. • Complete each step of the investigation. Below are hints for each step if you need them.

11. Step 1: Are the shapes the same or different? • How does the shaded portion of the shape change from one odd-numbered shape to the next?

12. Step 2: First, focus on the polygon shape. • Does the polygon change from one even-numbered shape to the next? • If so, how does it change? • Second, focus on the small circles inside the shape. • How do these circles change from one even numbered shape to the next?

13. Step 3: The next shape is the 7th shape. • Because it is an odd-numbered shape, use the patterns you described in Step 1 to figure out what it will look like. • The 8th shape is an even-numbered shape, so it should follow the patterns you described in Step 2.

14. Step 4: Notice that the odd-numbered shapes go through a cycle that repeats every eight terms. • So, for example, the 1st, 9th, and 17th shapes look the same; • the 3rd, 11th, and 19th shapes look the same; and so on. • Use this idea to figure out what the 25th shape looks like.

15. Step 5: How many sides does the 2nd shape have? • The 4th shape? The 6th shape? • The nthshape? • How many sides will the 30th shape have? • How will the dots be arranged on the 30th shape?

16. Inductive Reasoning process of observing data, recognizing patterns and making generalizations about those patterns. • Drawing conclusions based on experience • Ex: • Cause/effect • Turning on water • Riding a bike • "Geometry“ means measure of earth • Can you name Professionals who use inductive reasoning?

17. Conjecture • A generalization made with inductive reasoning (Drawing conclusions) • Example: Bell rings M, T, W, TH at 7:40 am • Conjecture? • The bell will ring at 7:40 am on Friday • Example: Chemist puts NaCl on flame stick and puts into flame and sees an orange-yellow flame. Repeats for 5other substances that also contain NaCl • Conjecture? • All substances containing NaCl will produce an orange-yellow flame • Mathematicians use Inductive Reasoning to find patterns which will then allow them to conjecture. • We will be doing this ALOT this year!!

18. Finding Patterns • Ex: 2, 4, 7, 11, ... • Rule? • Add the next consecutive integer • Next 3 terms? • 16, 22, 29 • Ex: 1, 1, 2, 3, 5, 8, 13, ... • Rule? • Add previous two terms (Fibonacci Sequence) • Next 3 terms? • 21, 34, 55 • Ex: 1, 4, 9, 16, 25, 36, ... • Rule? • Add consecutive odd numbers OR the perfect squares • Next 3 terms? • 49, 64, 81