1. Lesson 2

1.4. Discover

Mathematics 20-3 Module 4

Module 4: The Right Kind Of Triangles

 

Discover

 

This is a photo of a totem pole and a First Nation home.

Medioimages/Photodisc/Thinkstock

You may not have a totem pole outside your home; however, if a nearby power pole or light standard casts a shadow along a level stretch of ground on a sunny day, you can determine its height by using similar right triangles.

 

Try This 1

 

You will need a partner to help you and a measuring tape that has both SI and imperial units.

 

Step 1: On a sunny day, measure the length of the shadow cast by a power pole or light standard. At the same time, measure the length of the shadow cast by a vertical object of known height. The object could be a fence post, a hockey stick, or even your partner.

 

Step 2: Draw a diagram and record your measures. A sample diagram is shown below.

 

This is a diagram of two poles casting shadows and forming triangles.

  1. On your diagram, describe what objects you chose and the date and time of day when you took your measurements.

  2. Explain why the Sun’s rays shown in the diagram must strike the ground at the same angle in each triangle.

  3. Explain how you know the two right triangles are similar.

  4. Set up a proportion and solve for the height of the pole.

course folder Save your responses to your course folder.

 

Share 1

 

Share your responses to the questions in Try This 1 with a classmate or with a group of people.

 

How are your responses to the questions similar? How do your answers differ?

 

course folder If required, save a copy of your discussion in your course folder.