Analisi Matematica II Gianluca Ferrari Calcolo differenziale
Esercizi sul calcolo di gradiente, divergenza e rotore
Calcolare il gradiente delle seguenti funzioni:
a. π(π₯; π¦) = π₯2+ 2π₯π¦ β π₯π¦2
βπ(π₯; π¦) β (ππ
ππ₯;ππ
ππ¦) = (2π₯ + 2π¦ β π¦2; 2π₯ β 2π₯π¦) b. π(π₯; π¦) = π¦ exp(2π₯2)
βπ(π₯; π¦) = (4π₯π¦ exp(2π₯2) ; exp(2π₯2)) c. π(π₯; π¦) = π¦2πβπ₯
βπ(π₯; π¦) = (βπ¦2πβπ₯; 2π¦πβπ₯) d. π(π₯; π¦) = log(π₯2+ π¦2)
βπ(π₯; π¦) = ( 2π₯
π₯2+ π¦2; 2π¦ π₯2+ π¦2) e. π(π₯; π¦) = exp (π₯π¦)
βπ(π₯; π¦) = (1
π¦exp (π₯
π¦) ; β π₯
π¦2exp (π₯ π¦)) Calcolare il gradiente βπ e il Laplaciano Ξπ delle seguenti funzioni:
a. π(π₯; π¦; π§) = π₯π¦2+ π¦π§3 β π§2
βπ(π₯; π¦; π§) = (π¦2; 2π₯π¦ + π§3; 3π¦π§2β 2π§) Ξπ(π₯; π¦; π§) β div βπ =π2π
ππ₯2+π2π
ππ¦2+π2π
ππ§2 = 2π₯ + 6π¦π§ β 2 b. π(π₯; π¦; π§) = π¦ sen π§ + π₯ sen π¦
βπ(π₯; π¦; π§) = (sen π¦ ; sen π§ + π₯ cos π¦ ; π¦ cos π§) Ξπ(π₯; π¦; π§) = β sen π¦ β π¦ sen π§
c. π(π₯; π¦; π§) = βπ₯2+ π¦2+ π§2
βπ(π₯; π¦; π§) = ( π₯
βπ₯2+ π¦2 + π§2; π¦
βπ₯2+ π¦2 + π§2; π§
βπ₯2 + π¦2+ π§2)
= 1
βπ₯2+ π¦2+ π§2(π₯; π¦; π§)
Analisi Matematica II Gianluca Ferrari Calcolo differenziale
Ξπ(π₯; π¦; π§) =
βπ₯2+ π¦2+ π§2β π₯
2βπ₯2+ π¦2+ π§22π₯ π₯2+ π¦2+ π§2
+
βπ₯2+ π¦2 + π§2β π¦
2βπ₯2 + π¦2+ π§22π¦ π₯2+ π¦2+ π§2
+
βπ₯2+ π¦2 + π§2β π§
2βπ₯2 + π¦2+ π§22π§ π₯2+ π¦2+ π§2
=3(π₯2+ π¦2 + π§2) β π₯2β π¦2β π§2
(π₯2+ π¦2+ π§2)βπ₯2+ π¦2 + π§2 = 2
βπ₯2+ π¦2+ π§2 Calcolare la divergenza e il rotore dei seguenti campi vettoriali:
a. πΉ(π₯; π¦; π§) = (π₯π¦; π¦π§; π§π₯)
div πΉ = β β πΉ = ππΉ1
ππ₯ +ππΉ2
ππ¦ +ππΉ3
ππ§ = π¦ + π§ + π₯ rot πΉ = β Γ πΉ = det ( πΜ πΜ πΜ
ππ₯ ππ¦ ππ§ π₯π¦ π¦π§ π§π₯
)
= det (ππ¦ ππ§
π¦π§ π§π₯) πΜ β det (ππ₯ ππ§
π₯π¦ π§π₯) πΜ + det (ππ₯ ππ¦ π₯π¦ π¦π§) πΜ
= (βπ¦; βπ§; βπ₯) b. πΉ(π₯; π¦; π§) = (π₯2+ π¦π§; π₯π¦π§; π₯ + π§π¦2)
div πΉ = 2π₯ + π₯π§ + π¦2
rot πΉ = (2π¦π§ β π¦π₯; π¦ β 1; π¦π§ β π§) c. πΉ(π₯; π¦; π§) = (π₯ cos π§ ; π¦ sen π₯ ; π§ cos π¦)
div πΉ = cos π§ + sen π₯ + cos π¦ rot πΉ = (βπ§ sen π¦ ; βπ₯ sen π§ ; π¦ cos π₯)