Calculator form
Use one of three right-triangle solving methods. The form uses a responsive 3-column, 2-column, and 1-column field layout.
Example data table
| Method | Known values | Adjacent side result | Notes |
|---|---|---|---|
| Hypotenuse + Angle | Hypotenuse = 12, Angle = 35° | 9.8298 | Uses adjacent = hypotenuse × cos(θ). |
| Opposite + Angle | Opposite = 7, Angle = 40° | 8.3426 | Uses adjacent = opposite ÷ tan(θ). |
| Hypotenuse + Opposite | Hypotenuse = 15, Opposite = 9 | 12.0000 | Uses adjacent = √(hypotenuse² − opposite²). |
Formula used
Method 1: Hypotenuse and angle
Adjacent = Hypotenuse × cos(θ)
Use this when the hypotenuse and one acute angle are already known.
Method 2: Opposite side and angle
Adjacent = Opposite ÷ tan(θ)
Use this when you know the opposite side and the matching acute angle.
Method 3: Hypotenuse and opposite side
Adjacent = √(Hypotenuse² − Opposite²)
This is the Pythagorean approach for right triangles with two known sides.
Extra derived values
Area = ½ × Adjacent × Opposite
Perimeter = Adjacent + Opposite + Hypotenuse
Cosine Ratio = Adjacent ÷ Hypotenuse
How to use this calculator
- Select the solving method that matches the values you already know.
- Choose degrees or radians when your selected method needs an angle.
- Enter the given measurements and pick a decimal precision.
- Optionally add a unit label such as cm, m, or ft.
- Press Calculate Adjacent Side to view results above the form.
- Review the steps, graph, and derived geometry values.
- Use the export buttons to download CSV or PDF summaries.
FAQs
1. What is the adjacent side in a right triangle?
It is the side next to the chosen acute angle, excluding the hypotenuse. The exact side depends on which acute angle you reference.
2. Which triangles can I use with this calculator?
This calculator is designed for right triangles only. The formulas depend on a 90-degree angle and standard trigonometric relationships.
3. Which method should I choose?
Choose the method that matches the information you already have. If you know the hypotenuse and an angle, use the cosine method. If you know two sides, use the Pythagorean method.
4. Can I enter radians instead of degrees?
Yes. Select radians in the angle unit field before calculating. The page converts values correctly and still reports the solved acute angle in degrees.
5. Why must the angle stay below 90 degrees?
The chosen angle is an acute angle of a right triangle. Values outside that range do not fit the intended geometry setup.
6. Does the calculator support decimal measurements?
Yes. You can enter integers or decimals for sides and angles. The precision selector controls how many decimal places are displayed.
7. What does the graph help me understand?
It shows how the adjacent side changes as the angle or opposite side changes. The highlighted point marks your current solved case.
8. Why would I export CSV or PDF?
CSV files are useful for spreadsheets and analysis. PDF files are better for sharing, printing, homework records, and saved reports.