Dear aspirant, yes it is true that you must have passed mathematics during 12th.here's the basic eligibility criteria for doing graduation in economics from DU-

1. An aggregate of 60% marks or more in one Language from List A1, a combination of other best three elective subjects from Lists A and B.

2. Out of the best two chosen above, non-inclusion of Economics will lead to a deduction of 1% on the aggregate of the Best Four.

3. Inclusion of any subject other than those given in Lists A and B in the ―best two will lead to a deduction of 2.5% per subject on the aggregate of the Best Four.

Additional Eligibility - 

Applicants must have passed in Mathematics in the qualifying EXAMINATION.

All the best 

Hope this helps