Leonhard Euler
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Leonhard Euler (15 ga watan Aprelu 1707- 18 ga watan Satumban 1783) (lafazi: /leonard oy-lar/) ya kasance masanin lissafi ne dan kasar Switzerland, masanin limin physics, masanin ilimin taurari, masanin geography, masanin lissafin logic kuma injiniya, wanda ya kirkiri nazarin graph theory da kuma topology kuma ya binciko abubuwa masu tasiri matuka a rassan lissafi irinsu; analytic number theory, complex analysis, da kuma infinitesimal calculus.. Ya rayu mafi ransa a Rasha da kuma Jamus. Shine ya kirkiri mafi akasarin dabarun lissafi na zamani da kuma alamomi, wanda ya hada da alamomi na Mathematical Functions. Haka zalika kuma yayi fice ta hanyar ayyukansa a mechanics, fluid dynamics, optics, astronomy da kuma music theory.

Ana daukar Euler a matsayin masana lissafi na musamman a tarihi kuma mafi mafi mahimmanci a karni na 18. Masana lissafi da dama wanda suka rayu bayan mutuwar Euler sun tabbatar da muhimmancinsa a lissafi kamar yanda aka hakayo a maganan daga mafiya yawancinsu: Pierre-Simon Laplace ya bayyana tasirin Euler a fannin issafi: Karanci Euler," karanci Euler, shine mai gidanmu duka". Carl Friedrich Gaus ya rubuta cewa: "Nazarin ayyukan Euler zai dawwama a matsayin makaranta na musamman da rassa daban daban na lissafi, kuma babu wani abu da zai maye gurbin shi." Har wayau ana daukar Euler a matsayin wanda ya fi kowa samar da ayyuka masu inganci; ayyukansa guda 866 da sauran ayyuka na nan an tattara su a Opera Omnia Leonhard Euler, wanda idan aka kammala tattara shi zai kunshi juz'oi guda 81. Ya kwashe mafi akasarin rayuwarasa a Saint-Petersburg, Rasha da kuma Berlin, sannan daga baya kuma a babban birnin Prussia. 

Ana jinjina wa Euler da fito da harafin Girkanci  π (pi) don nuna ratio na circumference na cycle dangane da diameter ta, da kuma fara amfani da alamar f(x) a matsayin alamar lissafin function, da harafin i don bayyana imaginary unit, da kuma harafin Girka Σ (babban baki na sigma) don nuna tarawa, da kuma harafin Girka Δ don nuna finite differences, da kuma amfani da kananan bakake don nuna gefe-gefen triangle da kuma manyan baki don nuna kusurwowinsa. Shine ya bayar da ma'anar da ake amfani dasu a yanzu na; constant е, base na natural logarithm, wanda a yanzu ake kira da lambobin Euler.

Har wayau, Euler shine wanda ya fara amfani da  graph theory (a wani lokaci don warware matsalar  Seven Bridges of Königsberg). Ya shahara a dalilin ayyukansa wanda suka hada daga cikin nasarorinsa kamar haka: warware lissafi na  Basel problem, bayan bayyana cewa: adadin infinite series na squared integer reciprocals suna zama daidai π2/6 (the sum of the infinite series of squared integer reciprocals equaled exactly π2/6), da dai sauransu. A bangaren physics kuwa, Euler ya sake tsara sharuddan Newton akan physics (Newton's Law of Physics) zuwa sabbin sharudda a aikinsa mai juz'i biyu Mechanica don inganta bayani akan motsin jikkuna (motion of rigid bodies). Haka zalika ya bada gudummawa sosai acikin nazarin elastic deformations of solid objects.

Kuruciya 
An haifi Euler a ranar 15 ga watan Aprelun shekara ta 1707 a Basel, Switzerland, ga uba  Paul III Euler, fasto a cocin Reformed Church da mahaifiyarsa Marguerite (née Brucker) wanda daga cikin tsatsonta akwai malamai da dama na zamunan baya. Shine babba acikin 'ya'ya hudu na iyayensa, yana da kannai mata biyu, Anna Maria da Maria Magdalena, da kuma kani namiji, Johann Heinrich. Jim kadan bayan haihuwar Leonhard, iyalinsa sun tashi daga Basel zuwa birnin Riehen, kasar Switzerland. inda mahaifinsa ya zamo fasto a karamin cocin garin inda Leonhard ya kwashe mafi yawancin yarintarsa.

Tun yana yaro, mahaifin Euler ya kasance yana koyar dashi lissafi, wanda shima Jacob Bernoulli ya koyar dashi, shekarun da suka gabata a Jami'ar Basel. A lokacin da yake da shekaru takwas, an tura Euler don yayi rayuwa da kakarsa ta wurin mahaifiya, inda ya shiga makarantar Latin a Basel. Bugu da kari, Johannes Burckhardt ya harar da shi a gida, wani saurayi masan theology wanda ke da ra'ayin lissafi.

Acikin shekarar 1720, a lokacin da yake da shekaru sha uku a duniya, Euler ya fara karatu a Jami'ar Basel. Halartar jami'a acikin wadannan 'yan kananan shekaru ba abin mamaki bane a wancan lokacin.  Johann Bernoulli ya koyar dashi elementary mathematics, kanin marigayi Jacob Bernoulli (wanda ya koyar da mahaifin Euler a baya). Nan da nan  Johann Bernoulli da Euler suka san juna. Euler ya kirayi Bernoulli da cewa shine "Tarihin rayuwarsa".

Aiki

Saint Petersburg 
'Ya'yan Johann Bernoulli su biyu Daniel Bernoulli da kuma Nicolaus II Bernoulli sun fara aiki a Imperial Russian Academy of Sciences da ke Saint Petersburg a shekara ta 1725, kuma sun tabbatarwa Euler da cewa zasu ambace shi idan dama ta samu. A ranar 31 ga watan July 1726 ne Nicolaus ya mutu, bayan yayi fama da cutar appendicitis, inda ya kwashe kasa da shekara guda a Rasha. Bayan Daniel ya maye gurbin dan uwansa a fannin lissafi/physics,  sai ya nemi da a cike gurbin da ya bari da abokinshi Euler. Acikin watan Nuwamban 1726 ne, Euler yayi maza ya amshi aikin. Amma ya jinkirta zuwa gari Euler eagerly accepted the offer, but delayed making the trip to Saint Petersburg a dalilin cewa ya rigaya ya nemi matsayin farfesa a jami'ar kasar Basel, wanda daga bisani bai samu nasara  ba.

Euler ya isa garin Saint Petersburg a watan Mayun 1727. A bashi aiki a fannin lissafi. Ya zauna gida daya da Daniel Bernoulli wanda sukayi aiki tare. Euler ya lakanci harshen Rashanci, ya zauna a garin Saint Petersburg, sannan ya dauki aiki na biyu tare da sojojin ruwa na kasar Rasha.

Manazarta 

'Yan lissafin Switzerland
'Yan kimiyyan Switzerland