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A4-format til udskrift. - Aarhus Universitet

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3. TANGENTPLAN 25<br />

2.31. Test Laplaces ligning ☞ [S] 11.3 Partial derivatives<br />

Test<br />

Funktionen f(x,y) = 3x + 5y + 10 er en løsning <strong>til</strong> Laplace’s ligning<br />

Løsning<br />

Udregningen<br />

giver<br />

∂ 2 f/∂x 2 + ∂ 2 f/∂y 2 = 0.<br />

fx = 3, fxx = 0, fy = 5, fyy = 0<br />

fxx + fyy = 0<br />

3. Tangentplan<br />

Afkryds:<br />

ja nej<br />

<br />

3.1. Oversigt ☞ [S] 2.7, 2.9, 11.4<br />

Nøgleord og begreber<br />

✌ Tangentlinje for graf<br />

✌ Tangentplan for graf<br />

✌ Test tangentplan<br />

✌ Lineær approximation i en og flere variable<br />

✌ Test approximation<br />

✌ Differentiabilitet i flere variable<br />

✌ Differentialet af en funktion<br />

✌ Test differentialet<br />

3.2. Tangentlinje ☞ [S] 2.7 Derivatives<br />

Figur<br />

y<br />

(a, f(a))<br />

y = f(a) + f ′ (a)(x a)<br />

I ⊂ R, f : I → R<br />

f(x)<br />

3.3. Ligning for tangent ☞ [S] 2.7 Derivatives<br />

Definition<br />

Tangentlinjen for grafen for en funktion y = f(x) i et punkt (a,b), b = f(a) er linjen<br />

gennem (a,b), som indeholder tangentvektoren<br />

<strong>til</strong> grafen<br />

(1,f ′ (a))<br />

x ↦→ (x,f(x))<br />

x

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