So I came across this argument on Twitter, and upon checking the comments I found the archived page of textbooks issued by ISIS in the areas it used to control, among them the Mathematics books that's taught for "second grade of highschool" (so basically grade 11).
Obviously the book is in Arabic (that's also why the link is long), but you can still read the equations. Still, you can use DeepL if you want to read the questions, the text at the beginning of each chapter or other stuff
https://ia802901.us.archive.org/view_archive.php?archive=/14/items/manhejtaalim/03%20-%20%D8%A7%D9%84%D9%85%D8%B1%D8%AD%D9%84%D8%A9%20%D8%A7%D9%84%D8%A7%D8%B9%D8%AF%D8%A7%D8%AF%D9%8A%D8%A9-20180921T154918Z-001.zip&file=03%20-%20%D8%A7%D9%84%D9%85%D8%B1%D8%AD%D9%84%D8%A9%20%D8%A7%D9%84%D8%A7%D8%B9%D8%AF%D8%A7%D8%AF%D9%8A%D8%A9%2F02%20-%20%D8%A7%D9%84%D8%B5%D9%81%20%D8%A7%D9%84%D8%AB%D8%A7%D9%86%D9%8A%20%D8%A7%D8%B9%D8%AF%D8%A7%D8%AF%D9%8A%20-%20%D8%B9%D9%84%D9%85%D9%8A%2F%D8%A7%D9%84%D8%B1%D9%8A%D8%A7%D8%B6%D9%8A%D8%A7%D8%AA%20%D9%84%D9%84%D8%B5%D9%81%20%D8%A7%D9%84%D8%AB%D8%A7%D9%86%D9%8A%20%D8%B9%D9%84%D9%85%D9%8A.pdf
Disclaimer: I don't support the terrorist group and this question is purely out of curiosity