Why do I get an invalid triangle warning?
A triangle must satisfy the inequality that any two sides summed together exceed the third. If that rule is broken, adjust the inputs until it holds.
Step-by-step walkthrough
Triangle Calculator Guide
Use this companion guide beside the interactive calculator to make sure you understand the “why” behind every click. Each section includes the classroom explanation, student-friendly language, and quick practice prompts.
Before you start
Collect the data points listed below and double-check their units. Keeping an organized “givens” list is one of the fastest ways to reduce math errors and impress exam graders.
- geometry
- triangle
- angles
Detailed procedure
Step 1
Enter the three side lengths; units can be any consistent measure.
Step 2
Confirm the triangle is valid—if not, adjust the sides until the triangle inequality is satisfied.
Step 3
Read the perimeter, area, angle sizes, and detected triangle type.
Teaching & troubleshooting tips
Can I use this for right triangles?
Yes. If the inputs form a right triangle the tool labels it accordingly and still reports angles and area.