Solving right triangles worksheet for Geometry
Pick the ratio that joins the side you have to the side you want, then use a calculator. To find an angle, set up the ratio from two sides and use the inverse: sin⁻¹, cos⁻¹ or tan⁻¹. The special triangles, where the angles come out exact, are here too.
Also taught in Algebra 2 and Precalculus, each at its own level and with its own examples.
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Sigma Prep · sigmaprep.io/worksheets Name Solving Right Triangles Date Period Find each measure.
Free math worksheets at sigmaprep.io/worksheets© 2026 Sigma Prep |
Sigma Prep · sigmaprep.io/worksheets Name Solving Right TrianglesAnswer keyVersion 1 Date Period Find each measure.
Free math worksheets at sigmaprep.io/worksheets© 2026 Sigma Prep |
How to do these
A right triangle has legs and . Find the angle opposite the side of length , to the nearest degree
- The two legs are opposite and adjacent, so it is tangent: tan x = 7/10.
- x = tan⁻¹(0.7), which is 34.99 on the calculator.
The answer is .
Where students go wrong
Pressing tan when the question needs tan⁻¹. tan takes an angle and gives a ratio; to get the angle back from the ratio it has to be the inverse. Also check the calculator is in degree mode, or every answer comes out wrong.
Also called finding missing angles or inverse trig ratios.
What you can put on this worksheet
- A missing side, any angle, rounded
- Find the length to the nearest tenth. — a right triangle with a 47° angle, legs 13 and x, hypotenuse unknown →
- An angle from two sides, with inverse trig
- Find . Round to the nearest degree. — a right triangle with a θ angle, legs 20 and 13, hypotenuse unknown →
- The acute angles, exactly
- A right triangle has legs and . Find the larger acute angle. →
- Solve the whole triangle
- Solve right triangle with , , . Round sides to the nearest tenth. → , ,
- All three sides given: find the angle
- Use the three sides to find , to the nearest tenth of a degree. — a right triangle, labeled 34, 30, 16, θ →
- Triangles drawn any way round
- How long is the leg marked ? Give it to the nearest tenth. — a right triangle, labeled 39, x, 48°, D, E, F →
- The altitude splits it into two right triangles
- Find the length marked to the nearest tenth. — a triangle split into two right triangles by its altitude, labeled x, 26, 33°, 52° →