Integral not being computed
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I want to compute the integral of normDf between a and b. What am I doing wrong?
This is my code
syms t
assume(t, "real")
f1 = 3*t-t*t*t;
f2 = 3*t*t;
f = [f1, f2]
df = diff(f, t)
a = 0;
b = 1;
normDf = sqrt(df(1)*df(1)+df(2)*df(2))
int(normDf, t, a, b)
采纳的回答
Simplify normDf before applying int(). Don't know why int() doesn't do this on its own
syms t
assume(t, "real")
f1 = 3*t-t*t*t;
f2 = 3*t*t;
f = [f1, f2];
df = diff(f, t);
a = 0;
b = 1;
normDf = sqrt(df(1)*df(1)+df(2)*df(2))
normDf = simplify(normDf)
int(normDf, t, a, b)
更多回答（1 个）
David Hill
2022-3-4
use vpaintegral
syms t
assume(t, "real")
f1 = 3*t-t*t*t;
f2 = 3*t*t;
f = [f1, f2];
df = diff(f, t);
a = 0;
b = 1;
normDf = sqrt(df(1)*df(1)+df(2)*df(2));
vpaintegral(3*(4*t^2 + (3*t^2 - 3)^2/9)^(1/2), t, a, b)
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