Golden ratio to find radius of moon | Similarity | Geometry | Khan Academy

Practice this lesson yourself on KhanAcademy.org right now: https://www.khanacademy.org/math/geometry/similarity/cc-solving-prob-similar-tri/e/solving-problems-with-similar-and-congruent-triangles?utm_source=YT&utm_medium=Desc&utm_campaign=Geometry Watch the next lesson: https://www.khanacademy.org/math/geometry/similarity/cc-solving-prob-similar-tri/v/challenging-similarity-problem?utm_source=YT&utm_medium=Desc&utm_campaign=Geometry Missed the previous lesson? https://www.khanacademy.org/math/geometry/similarity/cc-solving-prob-similar-tri/v/triangle-similarity-in-pool?utm_source=YT&utm_medium=Desc&utm_campaign=Geometry 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. About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content. For free. For everyone. Forever. #YouCanLearnAnything Subscribe to Khan Academy’s Geometry channel: https://www.youtube.com/channel/UCD3OtKxPRUFw8kzYlhJXa1Q?sub_confirmation=1 Subscribe to Khan Academy: https://www.youtube.com/subscription_center?add_user=khanacademy

Comments

1. Uncanny, isnt it.... Coincidence?
2. The universe :P
3. Is this a joke?  Teaching at its very worse.  This is a non-sense problem about a contrived relationship about earth & moon.  It started very abruptly and went downhill from there. What's the intended point of this lesson?  BTW, the Earth & Moon in an approx 4/1 ratio (8000mi/2000mi).
4. mind equals blown!! great video sal!
5. Great but what's the answer? if I tell you that some object is moving at approximately pi squared meters per second that tells you almost nothing unless you happen to know how much pi squared is off the top of your head, but even then why bother if it's an approximation? why not say approximately 10 m/s instead?  6371(1.618^0.5 - 1) km is about 1732.95 km.  I would argue that this approximation is a better answer because the earth is being approximated as a sphere and it's radius is being approximated as 6371km.  Giving an exact radical answer isn't the most helpful in this context since the exactness gained is made meaningless by approximating, but a decimal approximation of the final answer is by contrast useful.  For those curious this differs from the actual value by about 0.25%
6. Question from a high school senior:
   
   Why is the side ME, or the side with the value sqrt of thi, turn into (6371)(sqrt of thi) when you convert the picture into km?
7. You mentioned a video about phi in the beginning but I have trouble finding it. Link please!
8. Pot-ASH-ium!!!
   Mag-ney-shium!!
9. Oblate spheroid
10. Please we Want IMO that's great !!!