Education Technology

# Activities

• ##### Subject Area

• Math: Geometry: Triangles

9-12

45 Minutes

• ##### Device
• TI-83 Plus Family
• TI-84 Plus
• TI-84 Plus Silver Edition
• TI-Navigator™

## Calculating the Area of a Triangle Using Heron's Formula

#### Activity Overview

Students will measure the lengths of the sides of three different triangles and apply Heron's Formula to calculate the area in acres. The measurements for this activity may be done outside or, using a specified scale, completed inside. Students will calculate the area using their graphing calculators. The teacher will use Navigator to access each student?s computations for comparisons and for determining where, if at all, any errors occurred.

#### Before the Activity

If outside set stakes connected by strings to form 3 adjacent triangles (two outside triangles will each share a common side with the inside triangle). The triangles need to be extremely large If inside place removable masking tape on the floor to draw the triangles with the outside triangles each sharing a common side with the inside triangle. Students will use a scale of 1 inch = 1 foot, or any scale the instructor may choose.

#### During the Activity

In pairs or triads, the students sketch the layout and will measure each side. Then calculate the area of each triangle using Heron?s formula where S is the semi-perimeter

#### After the Activity

Review student results and, as a class, discuss questions that appeared to be more challenging. Re-teach concepts as necessary.