Dear Aspirant,

there are many ways to join Indian Army at different post and maths is not compulsory to join Indian army.

After 12-

You can either participate in the Rally bharti of your state after 10th or you can give NDA entrance exam to Join Indian Army as a officer.

*In NDA exam there is separate section of maths test you need to pass, without this you will not able to clear the NDA written whether you have take maths in your 12th or not.

After Graduation-

there is CDS exam you can give to join Indian Army after completing your graduation from any stream with minimum 60% with a recognized university.

*there are also some other option to join Indian Army after 12th but for that you need to complete your graduation with a engineering degree.

Good Luck :)