How this is checked

Preparation material is worth nothing if it is confidently wrong, and a student who is studying a topic is the person least able to catch an error in it. So the maths here is checked by machine before it is published. This page says what those checks cover, and — further down, with the same prominence — what they do not.

What is checked

Every mathematical claim in the book, verified symbolically

408 claims

The 83 chapters carry 408 machine-checkable assertions — an integral's value, a limit, a determinant, a counterexample's arithmetic. Each is re-derived by SymPy, a computer algebra system, and the check runs as a build gate: a claim that does not verify blocks publication. It is not the author marking their own work, and it does not depend on anyone rereading carefully.

The verifier is deliberately allowed to answer “I cannot tell” as well as true or false. A verifier that guesses would eventually manufacture a defect in correct material, and a chapter edited to fix a fault that was never there is worse than an unchecked one.

Every formula, parsed by the renderer that displays it

all content

Question stems, options, explanations, chapter text, counterexamples and the per-option analysis are all pushed through the same KaTeX pipeline the site renders with. A formula that would break, or silently drop a symbol, fails the gate rather than reaching a page. Mathematics that renders wrongly is indistinguishable from mathematics that is wrong.

Every solved question, gated against the recorded answer

147 solved

All 147 previous-year questions here have a written solution, and 352 wrong options are analysed individually — not one worked solution repeated four times, but the specific mistake that produces each distractor. A solution whose marked answer disagrees with the recorded key is refused by the loader; it cannot reach the site.

Every linked lecture, confirmed to still exist

224 lectures

The video map points at 224 third-party lectures. Each id is resolved against YouTube's own metadata, so a video that has been deleted or made private is caught here rather than by a student hitting a dead embed. The videos are other people's work, linked and timestamped, never re-hosted and never put behind the paywall.

What is not checked

This is the part worth reading. Every limit below is real, and none of it is covered by anything above.

The answer key is transcribed, not machine-checked against CSIR's

The gate proves that a written solution agrees with the answer recorded for that question. It does not independently confirm that the recorded answer matches the official CSIR final answer key — that answer was entered by hand when the paper was transcribed. A transcription error would be reproduced faithfully by every check downstream of it.

So if you are deciding whether to trust this site, the right test is the obvious one: take a paper, compare the answers here against the official key, and check a derivation yourself. That test is worth running and nothing on this page substitutes for it.

Prose is not verified, only the mathematics

SymPy checks a computation. It cannot check whether an explanation is the clearest way to see something, whether a chapter emphasises what the exam actually rewards, or whether the stated reason a distractor tempts you is the real one. Those are judgement, and judgement is not gated.

Coverage is not completeness

83 subtopics, 83 chapters and roughly 77,000 words cover the syllabus, but 147 solved questions is a fraction of every paper ever set, and 149 counterexamples is not every counterexample that matters. Where something is thin, it is thin — the checks say nothing about how much exists.

Check it yourself

The strongest evidence is not on this page. Open a solved paper, pick questions at random, and compare the answers and the reasoning against the official key and your own working. If something here is wrong, it is worth telling us — a reported error is fixed for everyone who reads it afterwards.

Open the solved papers Browse the counterexamples Report an error

The counts on this page are read from the live site each time it loads, so they cannot drift from what is actually published. 398 published questions, 84 interactive visuals, 83 chapters.