matlab求定积分,请帮忙解释一下这是怎么回事,定积分不是应该是常数吗,为什么是带X的!>>symsX;>>fy=1.84*10^(-17)*X^6-7.115*10^(-23)*X^7-3.586*10^(-27)*X^8-7.575*10^(-13)*X^5+1.525*10^(-8)*X^4-0.0001752*X^3+1.1

Question

matlab求定积分,请帮忙解释一下这是怎么回事,定积分不是应该是常数吗,为什么是带X的!
>>syms X;
>> fy=1.84*10^(-17)*X^6 - 7.115*10^(-23)*X^7 - 3.586*10^(-27)*X^8 - 7.575*10^(-13)*X^5 + 1.525*10^(-8)*X^4 - 0.0001752*X^3 + 1.172*X^2 - 4266.0*X + 6.531*10^6;
>> df=diff(fy,X);
>> s=int(sqrt(df^2+1),X,7650,14550)
Warning: Explicit integral could not be found.
> In C:\MATLAB6p5\toolbox\symbolic\@sym\int.m at line 58

s =

int(1/5444517870735015415413993718908291383296000*(-592826091262412925646223236545697161897167167868933879129503881788141246201373998972928000*X+243788836981838604512389536075078229464211542160405824108055301718016000*X^6-17199258859148058798922578776264791727300818479839975812913692672000*X^7+836015684830162937057655846186206288647098436686564804263936000*X^8-2455042263422814359550191117417433970067890726631768352250006729234841600000*X^5+17623765259909929754913743816455340804773872726841283896722234675699145244672000*X^4-88467818098490634312132992461009158581373047709636339485620908443441427029950464000*X^3+295797993624507655235967093492635481959570306084275496869962857849943134473467751038976*X^2+369377216719355074893027274872661002458140508160000000*X^10+3181919480229446297889598125829423496167424000000*X^11-180413533967084666291167649647674454016000000*X^12-25696885005271077824881410766423093957900645217337344000000*X^9+847075396239762079191152580501104000000*X^13+24396043537121066792355686227515625*X^14+539461656205371589805588589676481055708173339218872031820038907690776863597233346445312000000)^(1/2),X = 7650 .. 14550)

>> double(s)
? Error: Assignment statements do not produce results. (Use == to test
for equality.)
Error in ==> C:\MATLAB6p5\toolbox\symbolic\@sym\double.m
On line 45 ==> D = reshape(eval(X),m,n);

Answer 1

运行没问题
>> clear;clc
syms X
fy=1.84*10^(-17)*X^6 - 7.115*10^(-23)*X^7 - 3.586*10^(-27)*X^8 - 7.575*10^(-13)*X^5 + 1.525*10^(-8)*X^4 - 0.0001752*X^3 + 1.172*X^2 - 4266.0*X + 6.531*10^6;
df=diff(fy,X);
s=int(sqrt(df^2+1),X,7650,14550);
double(s)
Warning:Explicit integral could not be found.
ans =
5.1925e+004
>>