Integration in m file

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Brian
Brian 2013-9-2
Really struggling with how integration works in matlab, I want to calculate the area under the function x+3 with limits 0 and where x+3 meets tan(x).
I have this but cannot get it to run.
thanks for any help
uplim = fzero(@(x) tan(x)-x-3,1.2)
function y=integrand(x);
y=(x+3);
I1=quad('integrand',0,uplim)
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Brian
Brian 2013-9-2
For clarity this is the original question:
"Calculate the area confined by the functions f(x)=x+3 and g(x)=tan(x) in the first positive interval. From x=0 to the first positive intersection point (where f(x)= g(x)). "
I may have misinterpreted it

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回答（1 个）

Roger Stafford
Roger Stafford 2013-9-3
Yes, I think you did misinterpret it. The question asks for the area "confined by the functions f(x)=x+3 and g(x)=tan(x)", not the area under f(x). You need f(x)-g(x) as an integrand. Make a plot of both functions and you'll see the difference.
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Brian
Brian 2013-9-3
编辑：Brian 2013-9-3
This is what I have:
uplim = fzero(@(x) tan(x)-x-3,1.2)
function y=integrand(x); y=((x+3)-tan(x)); end
I1=quad('integrand',0,1.3446)
I can get it to run seperately to get an answer but not in single file. Please help, thanks

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