A number of words ending in ‘ics’ which are plural in form, normally take a singular verb; e.g.

ACOUSTICS = the branch of physics concerned with the properties of sound. CLASSICS = a subject at school or university which involves the study of ancient Greek and Latin literature, philosophy, and history; e.g. an honours degree in Classics. ETHICS = the branch of knowledge that deals with moral principles. LINGUISTICS = The study of the nature, structure, and variation of language, including phonetics, phonology, morphology, syntax, semantics, sociolinguistics, and pragmatics

a) Mathematics is not an easy subject.
b) Mathematics is my favourite study.
c) Economics is one of the oldest of the social sciences.
d) Politics plays a big role in our life.

NOTE: But when these nouns are preceded by THE or any POSSESSIVE ADJECTIVE (my, our, your, his, her, etc.) they take plural verbs; e.g.

a) Her mathematics are weak.
b) Your mathematics are not very good.
c) The economics of the situation have yet to be explored. (means the economic facts)
d) What are his politics? (means his political views)