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Područje integracije u trostrukom     VIŠESTRUKI INTEGRALI     Cilindrične koordinate u trostrukom


Neposredna integracija u trostrukom integralu

Izračunajte integral $ \displaystyle \iiint\limits_{V}x^{3}y^{2}z  dx  dy  dz$ ako je

$\displaystyle V\ldots \left\{
 \begin{array}{c}
 0\leq x\leq 1  
 0\leq y\leq x  
 0\leq z\leq xy
 \end{array}
 \right.$   .    

Rješenje.

Trostruki integral neprekidne funkcije računamo slično kao i dvostruki integral [*][M2, poglavlje 4.3]:

$\displaystyle \iiint\limits_{V}x^{3}y^{2}z dx dy dz$ $\displaystyle =\iint\limits_{V_{xy}}x^{3}y^{2} dx dy\int\limits_{0}^{xy}z dz...
...\limits_{0}^{1}x^{3} dx\int\limits_{0}^{x}y^{2} dy\int\limits_{0}^{xy}z
  dz$    
  $\displaystyle =\int\limits_{0}^{1}x^{3} dx\int\limits_{0}^{x}y^{2} \left( \frac{z^{2}}{
 2}\right) \underset{0}{\overset{xy}{\bigg\vert}}dy$    
  $\displaystyle =\int\limits_{0}^{1}x^{3} dx\int\limits_{0}^{x}y^{2} \left( \fr...
...  dy=\int\limits_{0}^{1}x^{3} dx\int\limits_{0}^{x}
 \frac{x^{2}y^{4}}{2} dy$    
  $\displaystyle =\int\limits_{0}^{1}\frac{x^{5}}{2}\left( \frac{y^{5}}{5}\right) ...
...rt}}dx=\int\limits_{0}^{1} \frac{x^{5}}{2}
 \left( \frac{x^{5}}{5}-0\right) dx$    
  $\displaystyle =\int\limits_{0}^{1} \frac{x^{10}}{10}dx=\frac{x^{11}}{10\cdot 11}
 \underset{0}{\overset{1}{\bigg\vert}}=\frac{1}{110}$.