Question: Unexpected result for definite integral

I expected

int(x^(-13/10), x):
eval(%,x=1000)-eval(%,x=1/1000);

-(1/300)*1000^(7/10)+(10/3)*1000^(3/10)

but i get

int(x^(-13/10), x=1/1000..1000);

(1/30)*10^(9/10)*sin((3/10)*Pi)*(100*sec((1/5)*Pi)-csc((3/10)*Pi)*10^(1/5))

 

Can somebody explain why?

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