What is an exocyclic double bond?

I have been tasked to find the $\lambda\_{\text{max}}$ of 3,4-dimethyl-1,2,3,4,4a,5-hexahydronaphthalene.


[![enter image description here](https://i.stack.imgur.com/QkW8wm.png)](https://i.stack.imgur.com/QkW8w.png)


This was supposed to be fairly easy. I used the base value for homoannular diene ($\pu{253 nm}$) and added the increments for the three ring residues attached to the diene ($\pu{+(3\times 5) = +15 nm}$). This should get me a value of $\lambda\_{\text{max}}=\pu{268 nm}$. However, checking the solution this question, they have also added the increment for an exocyclic double bond, and have got the answer to be $\pu{273 nm}$ instead.


As far as I know, an exocyclic double bond means *exo*+*cyclic*, where *exo* means "outside" and *cyclic* means, well "cyclic", or more simply, a double bond that is outside the ring. I'm looking at this compound, and I dont see any exocyclic double bond at all.


Am I dealing with a key mistake here or is there something that I'm not aware of?




Surely you are aware that the calculation of this sort is but a very rough estimate, yet still I feel the urge to stress that once more. Having said that, let's look at the double bond in the first cycle: isn't it exocyclic with respect to *the other* cycle? 


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[![enter image description here](https://i.stack.imgur.com/OTsfv.jpg)](https://i.stack.imgur.com/OTsfv.jpg)


The double bond B is exocyclic to ring 2 as it is attached to an atom which is shared between ring 1 and ring 2 while the double bond A is not connected to any ring 2 atoms and is within just one ring, hence making it endocyclic


for further references visit <https://pharmaxchange.info/2012/08/ultraviolet-visible-uv-vis-spectroscopy-%E2%80%93-woodward-fieser-rules-to-calculate-wavelength-of-maximum-absorption-lambda-max-of-conjugated-dienes-and-polyenes/>


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