Hello aspirant,

YES, you can write Mathematics exam from NIOS board and you will be eligible for NATA exam. You are very much eligible for NATA (National Aptitude test in Architectural) if you pursuing your 12th standard from NIOS. NIOS is recognised board. You can be eligible for NATA if you have studied 12th standard with maths and scored 50% marks in aggregate .

The eligibility criteria for NATA exam is as follows :

Candidates should have passed 10+2 level or equivalent from a recognized board. OR Candidates who have passed 10+3 Diploma Examination with Mathematics as compulsory subject

Further, to know more about the NATA exam, you can follow the below mentioned link to know more about it : https://engineering.careers360.com/exams/nata

I hope that this will help.