The Tesla for lease or for sale you see at your local car dealership, find great deals on Tesla Leases and Lease Specials on the following Tesla models like Lease a 2015 Tesla Model S $838.00 mo, 2016 Tesla Model X $1,216.12 mo. Search now for Tesla LEASES for sale.
This cannot rigorously be described as sigma-pi conjugation since sigma and pi here refer to different defining planes, and interaction between orbitals of different symmetries (with respect to the same defining plane) is forbidden.
By definition, pi is the ratio of the circumference of a circle to its diameter. Pi is always the same number, no matter which circle you use to compute it. For the sake of usefulness people often need to approximate pi.