The minimum number of equal length subintervals needed to approximate $\int_1^2 xe^x\,dx$ to an accuracy of at least $\frac{1}{3}\times10^{-6}$ using the trapezoidal rule is
I am not sure of the solution,posting it from source http://www.cse.iitd.ac.in/~mittal/gate/gate_math_2008.html
question 21
It will be highly appreciable if anyone can explain it.