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Trigonometry

Sine, cosine and tangent: from right triangles to the unit circle, identities and periodic functions.

21 free sites · 18 in English.

1. Khan Academy – Trigonometry English khanacademy.org

   Ratios, unit circle, identities and equations.

   For: Middle & high schoolCollege

2. Khan Academy – Precalculus English khanacademy.org

   Trig functions, vectors and complex numbers.

   For: Middle & high schoolCollege

3. OpenStax – Algebra and Trigonometry 2e English openstax.org

   Free college textbook.

   For: College

4. OpenStax – Precalculus 2e English openstax.org

   Free precalculus textbook.

   For: College

5. Math is Fun – Trigonometry English mathsisfun.com

   Sine, cosine and tangent with animations.

   For: Elementary schoolMiddle & high school

6. Dave’s Short Trig Course English mathcs.clarku.edu

   Short, clear course from Clark University.

   For: Middle & high school

7. Trigonometry (Michael Corral) English mecmath.net

   Free trigonometry textbook.

   For: Middle & high school

8. Paul’s Online Notes – Cheat sheets English tutorial.math.lamar.edu

   Trig, algebra and calculus summaries.

   For: Middle & high school

9. Math Open Reference English mathopenref.com

   Animations of functions and triangles.

   For: Middle & high school

10. Purplemath English purplemath.com

    Trig lessons in plain language.

    For: Middle & high school

11. CK-12 – Trigonometry English ck12.org

    Interactive lessons and practice.

    For: Middle & high school

12. LibreTexts – Precalculus English math.libretexts.org

    Open precalculus and trig textbooks.

    For: College

13. Wikibooks – Trigonometry English en.wikibooks.org

    Free, open trigonometry textbook.

    For: Middle & high schoolCollege

14. Professor Leonard (YouTube) English youtube.com

    Full precalculus and calculus lectures.

    For: College

15. Brian McLogan (YouTube) English youtube.com

    Trig identities and equations.

    For: Middle & high school

16. Mathispower4u (YouTube) English youtube.com

    Short trig examples.

    For: Middle & high schoolCollege

17. The Organic Chemistry Tutor (YouTube) English youtube.com

    Trig problems worked out.

    For: Middle & high schoolCollege

18. Desmos Multilingual desmos.com

    Graph trig functions and their transformations.

    For: Middle & high school

19. GeoGebra – Graphing calculator Multilingual geogebra.org

    Explore the unit circle and graphs.

    For: Middle & high school

20. Desmos – Scientific calculator Multilingual desmos.com

    Free scientific calculator in the browser.

    For: Middle & high school

21. Paul’s Online Notes – Trig cheat sheet English tutorial.math.lamar.edu

    Every identity on two pages.

    For: Middle & high school