My maths faculty( who has experience of 12 year) did not taught me sub tangent and sub normal .He told us that it is not in syllabus and if it comes they will define it. So I should study it or leave it as i am left with very less time.
Leave it, no question was asked on it , in advanced ,not in syllabus, can come only in paragraph
I think it's given in books so if u have time you can read it or else leave it
Just see the concept of 'length of subtangent/subnormal' which comes in AOD.
Yes its length is in AOD only.
Yu may just by heart that formulas of lengths and also understand their basic definitions.Dont worry about derivations if yu have less time..even though it is present in some book .These formulas can be useful in AOD as well as DIFFERENTIAL EQN