Lesson Plan: Right Triangle Trigonometry: Solving for an Angle Mathematics

This lesson plan includes the objectives, prerequisites, and exclusions of the lesson teaching students how to find a missing angle in a right triangle using the appropriate trigonometric function given two side lengths.


Students will be able to

  • label the sides and angle of a right triangle,
  • find an unknown angle measure in a right triangle (given a figure) using the sine, cosine, and tangent ratios and their inverse functions,
  • draw a figure for a question and use it to find an unknown angle in a right triangle,
  • interpret and solve real-life and applied problems using right triangle trigonometry.


Students should already be familiar with

  • the Pythagorean theorem,
  • converting degrees into degrees, minutes, and seconds,
  • solving for a side in a right triangle using the trigonometric ratios (sine, cosine, and tangent),
  • the sum of interior angles in a polygon,
  • properties of polygons,
  • similar and congruent triangle properties.


Students will not cover

  • solving for a side only using trigonometry,
  • using the term inverse trigonometric functions,
  • non-right triangle trigonometry,
  • angles of elevation and depression.

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