https://onlinetestpad.com/ru/tests/trigonometry
http://matematestonline.narod.ru/testonline8-1.html
https://youclever.org/book/korni-1/
https://youclever.org/book/parallelnost-pryamyh-v-prostranstve-1/
https://www.youtube.com/watch?v=yCmO9o_784U
https://www.youtube.com/watch?v=ZQGJA2r-drU