1. Geometry: Similar Triangles

2. MA.912.D.11.5 Explore and use other sequences found in nature such as the Fibonacci sequence and the golden ratio. Block 30

3. Fibonacci sequence In mathematics, the Fibonacci numbers are the numbers in the following sequence: 1, 1, 2, 3, 5, 8, 13, 21 … By definition, the first two Fibonacci numbers are 1 and 1, and each remaining number is the sum of the previous two.

4. Fibonacci sequence: recurrence In mathematical terms, the sequence Fn of Fibonacci numbers is defined by the recurrence relation with seed values

5. Graph of consecutive values of Fibonacci sequence

6. Golden mean Ratios of consecutive values of Fibonacci sequence: F n+1 /F n Tend to a number – it is Golden Mean

8. Ratio of terms of Fibonacci sequence converge to the Golden mean

9. Approximation of Golden Rectangle

10. Golden triangle

11. A golden triangle is an isosceles triangle in which the two longer sides have equal lengths and in which the ratio of this length to that of the third, smaller side is the golden ratio:

12. Golden triangle Different description of a golden triangle is an isosceles triangle with angles 36 0, 72 0 and 72 0

13. Golden triangle: examples As an example of the appearance of Golden Triangles: the outside triangles of a pentagram are Golden Triangles.

14. Golden triangle: properties Position of Golden Triangles in regular pentagon

15. Golden rectangle, golden triangle and logarithmic spirals

16. Logarithmic and golden spiral In the logarithmic spiral the distances between the turnings increase in geometric progression In geometry, a golden spiral is a logarithmic spiral whose growth factor b is related to φ, the golden ratio

17. Approximation to Golden spiral

18. Steps in construction of logarithmic spiral ABC golden triangle ABD similar triangle to ABC – golden triangle

19. Steps in construction of aproximation of logarithmic spiral ABC golden triangle ABD similar triangle to ABC – golden triangle We will continue to construct similar triangles in this fashion

20. Can you recognize golden triangles?

21. Approximation of logarithmic spiral

22. Class discussion: Ask students to search the internet for Golden Ratio in Art and Architecture Groups presentation and discussion: how to enhance teaching with connection to art and architecture Holy Family by Michelangelo: