▁is ▁exactly ▁equal ▁to ▁R ba ▁which ▁is ▁the ▁response ▁at ▁location ▁b , ▁when ▁that ▁same ▁exc itation ▁is ▁applied ▁at ▁a . ▁This ▁applies ▁for ▁all ▁frequencies ▁of ▁the ▁exc itation ▁signal . ▁If ▁Hab ▁is ▁the ▁transfer ▁function ▁between ▁a ▁and ▁b ▁then ▁Hab   =   H ba , ▁if ▁the ▁system ▁is ▁linear . ▁ ▁In ▁the ▁special ▁case ▁of ▁a ▁modal ▁analysis ▁this ▁is ▁known ▁as ▁Max well ' s ▁reci pro city ▁theorem . ▁ ▁In ▁elect romagnet ism ▁the ▁concept ▁is ▁known ▁as ▁Lor ent z ▁reci pro city . ▁ ▁The ▁reci pro city ▁principle ▁is ▁also ▁used ▁in ▁the ▁analysis ▁of ▁structures . ▁When ▁combined ▁with ▁super position , ▁symmetry ▁and ▁anti - sym met ry , ▁it ▁can ▁be ▁used ▁to ▁resolve ▁complex ▁load ▁conditions . ▁ ▁References ▁ ▁Category : App lied ▁mathematics ▁Category : Engine ering ▁concepts <0x0A> </s> ▁Lieutenant ▁General ▁Sam i ▁Ha fe z ▁An an ▁or ▁En an ▁( , ▁; ▁born ▁ 2 ▁February ▁ 1 9 4 8 ) ▁is ▁an ▁Egypt ian ▁military ▁officer . ▁He ▁was ▁the ▁Chief ▁of ▁the ▁General ▁Staff ▁of ▁the ▁Ar med ▁Forces ▁from ▁ 2 0 0 5 ▁until ▁August ▁ 2 0 1 2 , ▁until ▁his ▁ret irement ▁was ▁announced ▁by ▁President ▁Moh amed ▁M ors i . ▁ ▁In ▁January ▁ 2 0 1 8 ▁he ▁announced ▁himself ▁as ▁a ▁candidate ▁in ▁the ▁ 2 0 1 8 ▁Egypt ian ▁president ial ▁election ▁before ▁being