Measuring the Diameters of the Moon at Perigee and Apogee

[crystalplane]

Homework Statement

the image below shows the Moonat perigee and apogee. Measure the diameters for the two, and determine the ratio between perigee and apogee idstance.Based on your result, what is the eccentricity of the Moon'orbit? Compare your value with the Moon' s mean orbital eccentricity(e= 0.0549)

Homework Equations

i have already measured diameters of apogee and perigee, 6.00cm and 13.00 cm(i am not sure about these two numbers.)

The Attempt at a Solution

based on the formula e= (1-b^2/a^2)^0.5,where b is the sei-minor axis...i am very confused about this question.
any help is appreciated.

 

[Janus]

You need to find a formula that relates eccentricity to apogee and perigee rather than to the semi-major and semiminor axi. (Or find a formula that relates the apogee and perigee to the semi-major and semi minor axi.)

I'd also double check your measurements. (they seem a bit off to me.)