Which of the following is equal to the length of the major axis of an ellipse?

A.The length of the minor axis
B. The sum of the focal radii
C. The value of a2 - b2
D. The eccentricity

Question

Which of the following is equal to the length of the major axis of an ellipse?

	A.The length of the minor axis
 	B. The sum of the focal radii
 	C. The value of a2 - b2
 	D. The eccentricity

anonymous · Answer

How would I do this or solve this?

mertsj · Answer

Let's do this one by elimination:
We know that the length of the major axis does not equal the length of the minor axis so A is out.

anonymous · Answer

yes, that's correct.

mertsj · Answer

I'm not sure what the focal radii are so B is a possibility

mertsj · Answer

a^2-b^2=c^2 for an ellipse and the length of the major axis is not c^2 so C is out.

anonymous · Answer

this is an example of D http://www.mathsisfun.com/geometry/images/eccentricity.gif

mertsj · Answer

The eccentricity is c/a and the length of the major axis is 2a so D is out and the answer is B

anonymous · Answer

the answer is B?

anonymous · Answer

Thanks @Mertsj for helping me through this.

mertsj · Answer

yes

mertsj · Answer

yw

mertsj · Answer

http://www.pierretoret.com/index.php/en/mathematics/372-plane-geometry/6072-focal-radii-of-an-ellipse

anonymous · Answer

oh thats what it is . thanks i didnt know that