MATLAB: I typed the anwer it gave me into a calculator and it is the correct value(147). Please tell me why it is giving it in such a long format. The following is finding the intergral of the fuction from a to b.

why is it giving it in this format? i tried a simpler intergral and it gave the short answer.

syms V
f=(636*V.^(-1.4));
R=int(f,V)
W=int((f),V,(3.75),(5.75));
W
R =
-1590/V^(2/5)
W =
(106*2^(4/5)*(23*15^(3/5) - 15*23^(3/5)))/23
>>

Best Answer

You used the Symbolic Toolbox function int(), which means that you deliberately asked the toolbox to find the closed form solution to the integral if it was possible to find the form. The result of the integration is not 147, it is a value approximately 147, exact solution given by W. If you want to see the approximate solution in decimal, you can vpa(W) or double(W)
To understand this you need to know that your V.^(-1.4) was converted to V.^(-7/5)
Symbolic integration treats floating point exponents as if they were rational numbers and does its best to find the resulting integral.
MATLAB does not treat exponents such as -1.4 as rational numbers. MATLAB defines Base^Exponent exponentiation in terms of exp(Exponent * log(Base)) -- which can have some very different results than rational exponents when dealing with negative or imaginary numbers.
You should probably have used numeric integration instead of using symbolic integration. See integral() for numeric integration.
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