What the site is
The center of the site is an interactive unit circle: drag a point and read every value, exact and decimal, in degrees and radians. Around it are tools that use the same circle: practice modes to learn it, printable blank and filled circles, calculators for reference and coterminal angles, the inverse sine, inverse cosine and inverse tangent, the law of sines and the law of cosines, plus a coordinate plane printable.
Every calculator shows its steps and draws the answer on the circle or on a triangle, because a number alone does not help much when you are learning.
Who makes it
Fernando Margareto is an independent creator of educational web tools and the founder and editor of Unit Circle Lab. Unit Circle Lab is run from Yátova (Valencia), Spain.
How the math is checked
All the math on the site comes from a single module that every tool shares. It is covered by automated tests that run before each update, including:
- the exact and decimal values of all six functions at the 16 special angles;
- reference and coterminal angles, including negative angles and angles past 360°;
- inverse functions, including the edges of their domains;
- triangles with known answers, including the ambiguous case with zero, one and two solutions.
Results are rounded for display. If something looks wrong, please get in touch: corrections are welcome and fixed quickly.
How the site works
- No accounts and no sign-up. Practice progress and settings stay in your own browser.
- All illustrations, diagrams and printables are drawn by the site’s own code; none come from stock image libraries.
- The site is free to use and is funded by advertising. Ads are kept away from the tools and never appear on printouts or PDFs.
Contact
Questions, corrections or ideas for a tool: use the contact form or write to info@unitcirclelab.com.