PreCalculus: Sum & Difference Practice

5.4: Sum and Difference Formulas
1. Login to SuccessNet (use the link on the Links menu)
2. click on PH Math 2004
3. Click on Chapter 14
4. Click on 14-6
5. Click on Interactivity
6. Open the Exploration Guide.
7. Complete the activity multiple times.

Geometry Honors: Chapter 4 Project

Tri, Tri Again

Have you ever wondered how bridges stay up? How do such frail-looking frameworks stretch through the air without falling? How can they withstand the twisting forces of hurricance force winds and the rumbling weight of trucks and trains? Part of the answer lies in the natural strength of triangles.

You will explore how engineers use triangles to construct safe, strong, stable structures. You then will have a chance to apply these ideas as you build your own structure. You will see how a simple shape often can be the strongest one.

Bridge Collapses
Sometimes engineering disasters happen.


Sunshine Skyway Bridge
Spans Tampa Bay on the West Coast of Florida

Collapse of the Sunshine Skyway Bridge spanning Tampa Bay, May 9th, 1980

Read about what happens when a structure is not strong and stable enough.
How would you have felt being in the white car pictured above?
"The Day the Skyway Fell", A special of the St. Petersburg Times on May 7, 2000

Audio recording of Mayday call made from the Sunshine Skyway Bridge Collapse, Tampa Bay, Florida, May 1980 (MP3 format) (updated URI, Jun 29 2005)

Activity 1: Modeling
Many structures have straight beams that meet at joints. You can use models to explore ways to strengthen joints.

• Cut seven cardboard strips approximately 6 in. by 1/2 in. Make a square frame and a triangular frame. Staple across the joints.
• With your fingertips, hold each model flat on a desk or table, and try to change its shape. Which shape is more stable?
• Cut another cardboard strip and use it to form a brace for the square frame. Is it more rigid? Why does the brace work?

Activity 2: Observing
Using the internet, find a picture (not drawing) of a bridge, tower, or other structure that has exposed frameworks. Print the picture. Highlight where triangles are used for stability.

Activity 3: Investigating
Building Bridges - Chicago Tribune
Visit this website and complete all of the activities up to and including "Engineering Rome"

In the first activity you tested the strength of two-dimensional models. Now investigate the strength of three-dimensional models.
Using toothpicks and marshmallows to construct a cube and a tetrahedron (a triangular pyramid).

Tetrahedron

Which model is stronger?
Describe how you could strengthen the weaker model.
Answer as a comment to the blog. Please sign your (first)name.
Remember to leave out any personal information.

Geometry Honors: 4.6 Congruence in Right Triangles

4.6 Congruence in Right Triangles
In Pairs
1. Login to SuccessNet (use the link on the Links menu)
2. click on PH Math 2004
3. Click on Chapter 4
4. Click on 4-6
5. Click on Interactivity
6. Open the Exploration Guide.
7. Record your answers on one piece of paper
8. Comment on this post with your findings. Remember to sign your (first)name.