This all-inclusive site covers everything geometry, split up into bite-sized pieces. Books One and Two have solid information and a quick search for "triangle" will get you what you need to know.
This is a comprehensive and straightforward website dedicated to trigonometry exclusively. It's separated into short sections, but it covers a lot of valuable information in a good, approachable way.
If you can't get enough of proofs or Pythagoras, then you might be interested in the many, many, many different ways you can prove the Pythagorean theorem. Pick your favorite!
Answer these nine challenging questions using the Pythagorean theorem, discover the password, and win the treasure. Have you got what it takes?
A series of videos explaining the most important elements of geometry and trigonometry as well as how they're applicable in everyday life. Ever considered a career in geometry or trigonometry? These PhD's have got your back.
Educational videos explaining trigonometry and its slightly more complicated side including graphs, radians, and trigonometric identities. These snippets can give you a good feel for what trigonometry is all about, and help supplement our understanding.
This little doodad can be useful in checking your work. It'll solve any triangle for us, and all we have to do is input the information we know already. It applies the same theorems and laws we learned, but it's way faster.
Enter your name and start playing jeopardy—Pythagorean theorem style. This is a great way to make use of the Pythagorean theorem for those who have a little trouble with it or just want the extra practice.
This interactive activity helps visualize the relationship between the Pythagorean theorem and the Law of Cosines using squares and triangles. It really nicely melds the geometry and trigonometry, allowing us to see how the shapes affect the numbers.
Play this neat game and use a bunch of items, logic, and trigonometry to escape from a room. It's tangentially related, but still a whole lot of thought-provoking and sometimes frustrating fun.