I needed a refresher on trig last year for some robotics simulations I was working on. The trig lesson was extremely helpful: <a href="http:&#x2F;&#x2F;betterexplained.com&#x2F;articles&#x2F;intuitive-trigonometry&#x2F;" rel="nofollow">http:&#x2F;&#x2F;betterexplained.com&#x2F;articles&#x2F;intuitive-trigonometry&#x2F;</a><p>And fwiw, I finally learned an intuitive understanding of radians by reading the Tau Manifesto (not on BetterExplained). It would be awesome if BetterExplained used tau instead of pi in the lesson on radians, but that&#x27;s a minor nitpick for a very helpful set of lessons.