 WSP Area of Triangles

• ## Area of Triangles

Grade: 3rd to 5th, 6th to 8th

How Do You Find the Area of a Triangle?

To find the area of a triangle, find a way to make it look like a shape for which you already know how to find the area. Try to make a parallelogram using a copy of the triangle.

### Instructions

The goal is to create a parallelogram by using a copy of any triangle.

• Change the size and shape of triangle ABC by dragging points A, B, and C.
• Click the Create Copy button to make a copy of the purple triangle. Translate the yellow copy using point C, and rotate it using point B'.
• The Construct Parallelogram button will complete the problem for you.
• The Show Dimensions button indicates the dimensions needed to find the area, and Show Area button will show the area of triangle ABC.
• The Reset button will allow you to start over.

### Exploration

Use the Create Copy button to create a yellow copy of the purple triangle. Try to arrange the two triangles to form a parallelogram. If you need help, the Construct Parallelogram button will show one way of making a parallelogram. There are also two other ways—can you find them?

• What measurements on the triangle do you need to make in order to find the area of a parallelogram?
• What is the area of the triangle?

### Objectives and Standards

NCTM Standards and Expectations
• Geometry / Measurement
• Understand that by similarity, side ratios in right triangles are properties of the angles in the triangle, leading to definitions of trigonometric ratios for acute angles.
• 3-5
• 6-8
• Geometry
• Measurement