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Unit 7 · Right Triangles and Trigonometry

7.7Sine, Cosine, and Tangent

Quick Answer

For an acute angle θ in a right triangle: sin θ = opposite/hypotenuse, cos θ = adjacent/hypotenuse, tan θ = opposite/adjacent. Remember with SOH-CAH-TOA.

Essential Question

How do the sine, cosine, and tangent ratios each relate a specific pair of sides to an acute angle in a right triangle?

Learning Goals

  • 1Define sine, cosine, and tangent for an acute angle.
  • 2Set up trig ratios from a right triangle diagram.
  • 3Use a calculator to evaluate trig ratios.
  • 4Find a missing side using a trig ratio.

Key Vocabulary

Sine (sin θ)

opposite / hypotenuse.

Cosine (cos θ)

adjacent / hypotenuse.

Tangent (tan θ)

opposite / adjacent.

SOH-CAH-TOA

Mnemonic for the three primary trig ratios.

Full lesson content coming soon

Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.