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**1. Homework Statement**

The question says that :

A planet of mass ##m## moves along an ellipse around the sun so that its maximum and minimum distances from the sun are equal to ##r_1## and ##r_2## respectively. Find the angular momentum ##M## of this planet relative to the centre of the sun.

**2. Homework Equations**

##mv^2/r=GMm/ r^2##(I dont know how to use fractions in latex)

**3. The Attempt at a Solution**

What I did:

##r_1+r_2=a##=semi major axis of the ellipse

And using the given equation:

##v=√(Gm_s/a)## since the semimajor axis length is used in this formula.

Now to find the angular momentum ##M=mvr##

But I don't know which ##r## iinto be used here. The answer is ##m√(2Gm_sr_1r_2/a)##. So can we say that ##r_{eff}=√2(r_1r_2)##?