There are several online resources and video lectures available for Mathematics optional for UPSC preparation. These resources can be beneficial for candidates who have chosen Mathematics as their optional subject and are looking for additional study material and guidance. Here are some details about these resources:

1. EduRev:
EduRev is an online learning platform that provides comprehensive study material, video lectures, practice questions, and previous year papers for various competitive exams, including UPSC. It offers a dedicated section for Mathematics optional, where candidates can find a wide range of resources to enhance their preparation.

- Video Lectures: EduRev provides video lectures by experienced faculty members who cover the entire syllabus in a structured manner. These lectures help in understanding complex concepts, problem-solving techniques, and exam-oriented approach.

- Study Material: The platform offers well-organized study material that covers all the topics of the Mathematics optional syllabus. It includes detailed explanations, examples, and practice questions to strengthen the conceptual understanding of the subject.

- Previous Year Papers: EduRev also provides access to previous year question papers of the Mathematics optional. Solving these papers helps in understanding the exam pattern, marking scheme, and important topics.

2. YouTube Channels:
There are several YouTube channels that offer free video lectures and tutorials for Mathematics optional. Some popular channels include:

- "Maths Optional by Manoj K. Jha": This channel provides video lectures by Manoj K. Jha, an experienced faculty member. The lectures cover various topics of the Mathematics optional syllabus and focus on problem-solving techniques.

- "Mathematics Optional by Alok Ranjan": In this channel, Alok Ranjan, a renowned faculty member, delivers video lectures on different topics of Mathematics optional. The lectures are interactive and cover both theory and numerical aspects of the subject.

3. Online Forums:
Participating in online forums and discussion platforms can also be beneficial for Mathematics optional preparation. These platforms allow candidates to interact with fellow aspirants, share study resources, clarify doubts, and discuss important topics. Some popular online forums include UPSC Forum, Quora, and Reddit.

In conclusion, candidates preparing for UPSC Mathematics optional can avail various online resources and video lectures provided by platforms like EduRev and YouTube channels such as "Maths Optional by Manoj K. Jha" and "Mathematics Optional by Alok Ranjan". Additionally, participating in online forums can also enhance the overall preparation process.