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Web skærmformat. - Aarhus Universitet

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I. Differentiation – 5. Gradient 96<br />

y<br />

u<br />

(cos ,sin )<br />

5.14. Retningsafledt ☞ [S] 11.6 Directional derivatives and the . . .<br />

Eksempel 2<br />

Den retningsafledede af<br />

f(x,y) = x 3 − 3xy + 4y 2<br />

i punktet (x,y) i retning π<br />

6 er<br />

Specielt er<br />

Duf(x,y) = fx(x,y)cos π π<br />

+ fy(x,y)sin<br />

6 6<br />

= (3x 2 √<br />

3<br />

− 3y) + (−3x + 8y)1<br />

2 2<br />

Duf(1,2) = −3√ 3<br />

2<br />

1<br />

x<br />

+ 13<br />

2

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