This is a fun little geometry problem inspired by a suggestion from Yossi Rozhenko. If the red area equals the blue area, what is the value of: (large circle's radius)/(small circle's radius)?

Small correction: At 3:07 I should have said "4 minus pi."

My…

In this video I'm presenting a neat proof that e is irrational, using only calculus techniques, although I'm not even using that much calculus. It's elementa...

In this video, Oon Han shows the following trigonometric identities,
double angle identity for sine,
double angle identity for cosine, 3 version,
power reduction for sin^2(x),
power reduction for cos^2(x),

Hope you guys enjoy the video. Please like…

Follow the simple instructions in the video and the result will be a fun mathematical effect! The trick got really popular a couple of years ago, but no one explained exactly why it worked. So in this video I also give the reason why the effect works out.…

Será que esse povo aí na praia sabe quem é o Kostrikin?

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double angle identities, power reduction identities, by Oon Han, https://youtu.be/6XmbiKGCK14

harmonic addition theorem…

In this video I find an antiderivative of arctan(sqrt(x)), which is surprisingly not hard to find! All you do is use a substitution and an integration by parts. Enjoy!