The subject is quite nice. It essentially covers most of the things you were meant to learn in high school as well as a few additional things.
It covers it in a way that is far superior to high school though and you often find yourself thinking "Why the hell did they teach it to me in such a stupid way in high school it is so much easier this way"
I would not say it is "heavy" but as with all maths subjects it is not entirely easy either.
The textbook when I did it was "Precalculus: mathematics for calculus" which I found to be a very well written book.
If it is still the same book tell your friend to buy it from me as I am trying to sell it
It is a hardcover so its in basically new condition.
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"Knowledge has much better uses than self-pity and superiority"