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Re: definite integral
Posted:
May 26, 2014 3:19 AM


On 04.05.14 23:28, Roger Stafford wrote: > "semiha" wrote in message <lk4s60$1aj$1@newscl01ah.mathworks.com>... >> i have defined as a symbolic x and t >> c=(abs([(1  4*(1 +2*i*t)/(1 +4 *( x)^2+4*(t^2)))]))^2 >> such a function i want to integrate this function which x from 300 to 300 and write >> a= int(c,x,300,300) >> and ezplot(c,t) >> but matlab doesn't calculate "a" and doesn't plot >           > I am not sure what is causing your trouble. The integrand can be expressed as the equivalent expression without complex numbers: > > c = 16*(1+4*t^2)/(1+4*t^2+4*x^2)^28/(1+4*t^2+4*x^2)+1
Only if you assume t to be real. If you do that, MATLAB has no problem with the integral, either:
>> syms x t real >> c=(abs([(1  4*(1 +2*i*t)/(1 +4 *( x)^2+4*(t^2)))]))^2; >> a = int(c,x,300,300)
a =
4800/((4*t^2 + 1)*(4*t^2 + 360001)) + 64*t^2*(300/((4*t^2 + 1)*(4*t^2 + 360001)) + atan((300*(8*t^2 + 2))/(4*t^2 + 1)^(3/2))/(2*(4*t^2 + 1)^(3/2)))  (32*t^2*atan(600/(4*t^2 + 1)^(1/2)))/(4*t^2 + 1)^(3/2) + 600
>> a = simplify(a,'Steps',1000)
a =
4800/(4*t^2 + 360001) + 600
HTH,
Christopher



