7.5 Conic Sections

[STARTS AT 24:37]

Instructor: So let's determine the eccentricity of this ellipse. 

Now, I can tell you what the minor access is. The minor axis is horizontal. And the major axis is vertical in this one because of the positions there. Ok, 25 is larger. That is in the vertical direction. 

So my a value is 5. And my b value is 4. Now, with an ellipse, this is not the right form, but with an ellipse, we can find c squared or c by saying c squared equals a squared minus b squared. So that will be 25. Let's write this as 5 squared minus 4 squared, which would be 25 minus 16, which is 9. So c is 3. 

So the eccentricity is c divided by a. 3 divided by 5, which is 0.6. Certainly that is less than 1. This is in fact an ellipse. We already knew that to begin with, but we can use that fact. 

[ENDS AT 25:46]