21st Century Lessons

Area of Right TrianglesMrs. Thompson

Level 1

1

Agenda:OBJECTIVE: SWBAT determine the area of any right triangle and defend their method.

1) Warm Up

3) Launch – Strategies for Explore

4) Explore – Problem Set (Partners & Groups)

5) Summary – Share Solutions & Expand

6) Assessment – Find the Area

2) Getting Ready – Geometry Puzzles

7

Launch

Agenda

12

This is a right triangle.

What is the area of this right triangle? How do you know?

How can you show your work/prove your answer?

What is a right triangle?

A right triangle is a triangle that has one 90⁰ angle.

= 1 square unit

Launch

Agenda

13

What is the area of the shaded region?

How do you know?

How can you show your work/prove your answer?

Explore – Understanding the Strategy

Agenda

16

Angela’s Strategy

1)Draw a “surrounding rectangle”

2)Determine the area of the rectangle

3)The area of the triangle is half the area of the rectangle!

Do you understand Angela’s strategy?

Explore - More

Agenda

17

1-Partners

2-Strategy Check3-Groups

Part 3 - (10 Min)

Finish the worksheet in GROUPS

Use Angela’s Strategy to find the area of the remaining triangles on the worksheet.

Summary (Part 1)

Agenda

18

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To Explore

Explain the Strategy

Turn and Talk: •Lefty, tell Righty the strategy for finding the area of ANY right triangle. •Righty, tell Lefty the strategy.

Common Language:1.Can you explain the strategy we learned that will work for finding the area of ANY right triangle?2.Why does this strategy work?

Summary (Part 2)

Agenda

35

Summary (Part 2)

Agenda

36

Expand your ThinkingDoes this strategy work when there are no grid lines?

Summary (Part 2)

37

Area of “Rectangle”: 5 ft x 10 ft = 50 ft2

Area of Triangle50 ft2 ÷ 2 = 25 ft2

5 ft

10 ft

Try It (As a Class): Draw and label a triangle with a base of 5 ft and a height of 10 ft. Then find the area.

Hmmm…

Oh yeah… Half of 50 is 25!

Agenda

Summary (Part 2) Independent Practice

38

Area of “Rectangle”: 8 in x 3 in = 24 in2

Area of Triangle24 in2 ÷ 2 = 12 in2

3 in

8 in

#1) Draw and label a triangle with a base of 8 in and a height of 3 in. Then find the area.

Hmmm…

Oh yeah… Half of 24 is 12!

Agenda