Right Triangle Trigonometry
Mystery Detective Worksheets · Grades 9–11 · Sine Cosine Tangent
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Inside the case file
Right triangle trigonometry activities, SOHCAHTOA worksheets, and sine, cosine and tangent practice for high school Geometry are all included in this Mini Mystery Detective pack of math worksheets. Students find the missing side or the missing angle of each right triangle, then use their answers to eliminate suspects and unmask the villain. Perfect for a trig ratios unit, geometry review, math centers, early finishers, sub plans, test prep and homework, and completely no prep - just print and go.
Every triangle is drawn and labeled, so no measuring or construction is needed. The cases build in order: sine first, then cosine, then tangent, then finding the hypotenuse, then a mixed page, and finally two pages of inverse trig where students work backwards from two sides to the angle.
What's Inside
- Using sine to find the side opposite a given acute angle when the hypotenuse is known
- Using cosine to find the side adjacent to a given acute angle when the hypotenuse is known
- Using tangent to find a missing leg from the other leg and the angle
- Finding the hypotenuse by rearranging the ratio and dividing rather than multiplying
- Choosing the correct ratio for yourself on a mixed page where all six arrangements appear
- Using inverse sine and inverse cosine to find a missing angle from two known sides
- Using inverse sine, inverse cosine and inverse tangent together on one page
- Identifying the hypotenuse, opposite and adjacent sides relative to the marked angle, with triangles drawn in every orientation so the labels cannot be guessed from position
- Rounding lengths to the nearest tenth and angles to the nearest whole degree
- Red-ink answer keys for every case
Seven detective cases to solve: The Roof Pitch Puzzle, The Flagpole File, The Sign Post Swap, The Zip Line Zigzag, The Drawbridge Dodge, The Crane Arm Caper and The Radar Room Ruse. Answer keys included for every case.
What is a Mini Mystery Detective?
A Mystery Detective is a print-and-solve detective activity - like a classroom escape room without the locks or the prep. Every answer matches one suspect's ID badge, so each triangle a student works out crosses another name off the list. The badge left unmatched at the end belongs to the villain, which makes the page self-checking: if two suspects are still standing, something needs another look. Real skill practice, critical thinking, and a detective hook that keeps the whole class working.
When to Use This Resource
- Right triangle trigonometry unit practice and end-of-unit review
- Geometry review before state testing
- Math centers and small groups
- Bell ringers and warm-ups
- Early finishers and enrichment
- Substitute teacher plans
- Homework and spiral review
- Revision before Algebra 2 or Precalculus
Grade Levels
Designed for 9th and 10th grade high school Geometry. Also beneficial for advanced 8th graders meeting the trigonometric ratios early, for 11th and 12th graders revisiting right triangle trigonometry before Algebra 2 or Precalculus, and for any student who needs more practice choosing between sine, cosine and tangent.
Why Teachers Love Mystery Detectives
- Zero prep - print and hand out
- Self-checking, so students catch their own mistakes before you do
- Only two sides or one side and one angle are ever labeled, so a trigonometric ratio is genuinely required rather than optional
- Each triangle is drawn to its own scale, so the missing side or angle has to be calculated and cannot be measured off the page
- Right angles appear in all four corners of the figure, so students must identify the hypotenuse rather than assume it
- Seven separate cases, so the pack covers a whole run of lessons rather than a single sheet
- Detective storyline keeps reluctant mathematicians working to the last question
- Works for independent practice, partners, small groups or a whole-class challenge
Pairs perfectly with the Pythagorean Theorem Mystery Detective, the natural lead-in to right triangle trigonometry.
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