Algebra II Lesson

How Tall Is That Tower? — Unlocking Right Triangle Trigonometry

Shared by A STEM Educator

10th & 11th Level II3-act-mathCCSS.MATH.HSG.SRT.C.860 min

Learning Objective

Students will be able to identify and correctly apply the sine, cosine, and tangent ratios in right triangles to solve for unknown side lengths and angles in real-world contexts (CCSS.MATH.HSG.SRT.C.8).

Lesson Overview

Students use a real-world photo of a cell tower to estimate its height through proportional reasoning, then discover and apply sine, cosine, and tangent ratios to calculate the exact height. The lesson culminates with inverse trig extensions connecting angle-finding to real design problems.

Materials

Printed or projected Act 1 photo of cell tower
Rulers (for proportional estimation)
Scientific or graphing calculators
Scaffolded graphic organizer (one per student)
Whiteboard/markers for group work
Desmos (projected for class graph reveals)
Exit slip half-sheets (printed)

Scaffolded Task Progression

1Task 1

Look at the photo of the cell tower. Using the technician (≈ 6 ft tall) as your only scale reference, estimate the height of the tower. Record: Too Low / Too High / Best Guess. Explain in one sentence how you reasoned.

2Task 2

After sharing estimates, discuss: What additional information would make your estimate more precise? List at least 2 specific measurements or facts you wish you had.

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