How to get from IAS in MPH to KCAS using POH graph of best TAS/GPH? My understanding is that in order to find the V(L/D)max I can do the following steps:


Look in the Pilot's Operating Handbook (POH) and find the performance reflecting the best TAS/fuel flow.
Find the KTAS for the determination from step 1.
Use a flight computer to get the KCAS from step 2.
The number from step 3 is V(L/D)max.
V(L/D)max / 1.316 = Vbe
V(L/D)max * 1.316 = V-Carson


While this sounds logical, I do not see any clear path from step 1 to step 2.

I looked up the definition of TAS, and it is related to EAS.  But when I look up EAS, it is dependent on TAS.  So when you do the algebra, it simplifies down to TAS = TAS and EAS = EAS, which is nonsensical, circular, and unhelpful.  Maybe I am not looking at the right equations, I’m not sure.

Do most pilots have flight computers with which they can determine KCAS starting with the value described in step 1?  If not, how should this best be done?  I could estimate air pressure using altitude, though it would not be very accurate, but I feel like there must be a better way given the large amount of instruments and tools available to most pilots in the cockpit.
Several questions here that need answers;
V(L/D max) is best glide speed.  Look it up under emergency procedures in the POH.
Airspeeds:
TAS is EAS corrected for temperature.
EAS is CAS corrected for compressibility.
CAS is IAS corrected for installation errors.  

IAS/CAS correction is available from the POH.
Pilots can use an E6-B flight computer to convert between CAS, EAS, and TAS.  

For more on this topic; here's a good link