1/r=r1+r2 ?

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Answer 1 · 2015-10-23T18:35:28

#r = (r_1r_2)/(r_1+r_2)#
Depending on what your question means!

Assumption:
r1 -> #r_1#
r2-> #r_2#

Then we have:

#1/r = 1/(r_1) + 1/(r_2)#

giving:

#1/r = (r_2 + r_1)/(r_1 r_2)#

To find r invert the whole equation giving:

#r = (r_1r_2)/(r_1+r_2)#

Is this what your question means?