Spotting Triangles - Intro to Physics - Circumference of Earth - Udacity

Uploaded by Udacity on 25.06.2012

All right.
So, we timed a camel and got the distance d.
Maybe not the most accurate of the odometers, but, hey.
We'll talk about error later, and we'll go with this for now.
The distance he measured was 5,000 stadia--we see that strange unit popping up again.
Now we just have to get α, which will require trigonometry--
the study of triangles, specifically right triangles.
Now, before we get jumping into the study of right triangles,
let's just quickly show where they're going to show up in this problem.
I mentioned before that if someone were standing here--
I'm going to represent someone standing by vertical black line--
he would cast a shadow like this.
You see--straight line, right angle--90-degree angle--straight line,
and we can imagine the sun's ray
completing the triangle.
Now, hidden in this right triangle are the mysteries of the circumference of the earth.
Let's figure out what's going on inside a right triangle.