Equation for a circle using the Pythagorean Theorem | Circles | Geometry | Khan Academy

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Geometry on Khan Academy: We are surrounded by space. And that space contains lots of things. And these things have shapes. In geometry we are concerned with the nature of these shapes, how we define them, and what they teach us about the world at large--from math to architecture to biology to astronomy (and everything in between). Learning geometry is about more than just taking your medicine ("It's good for you!"), it's at the core of everything that exists--including you. Having said all that, some of the specific topics we'll cover include angles, intersecting lines, right triangles, perimeter, area, volume, circles, triangles, quadrilaterals, analytic geometry, and geometric constructions. Wow. That's a lot. To summarize: it's difficult to imagine any area of math that is more widely used than geometry.

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[syko-]

finally i understand how circle equation com e from, you do me a very big favor thank u!!!

[ItzDinoFlower]

OMG THANK YOU SO MUCH!!! I have been struggling with my homework for hours until this video!!! Thank you!

[PhysicsOfParkour]

Just Amazing; just shows how Interrelated Mathematics is!!
Thanks Sal 

[ahmedsaad]

You changed ur voice at the ending. Very helpful.

[ryanio]

Fantastic explanation! Thank you so much Sal!

[lizzy]

This is great as usually it is hand waved away

[onlymoney]

so when doing it in the pythegoream the base of the triangle is always x?

[poonamlather]

Thank you so much you have made my life T~T

[anoirtrabelsi]

Great but it will be even better if you solve some IMO problems !!!

[kaisontoro]

I can't seem to find this video on khanacademy.org, I think it's been taken down for some reason

[THETHPHANTOM]

Lucky kids of the future. there is really no reason to not be top of the class, if you wanted to.

[Gtr]

All I can think about is how the example looks like a Smash Bros. logo.

[Soramix]

How did you get the answer? I still don't understand :(

[NickBurden]

why isn't (x-h)^2 + (y-k)^2  = r^2  the same as  (x-h) + (y-k) = r ?  Surely if you square root both sides, the new equation is the same?

[master_Wizard]

Why don't they teach this at school? It seems that the definition of education in high school is to throw you a bunch of equations to remember without knowing the how? or why? they work.