These lessons were made before the formular sheet was re-introduced, since then the expectation is for the formula sheet to remain available until 2030. Using SOHCAHTOA given in the lessons is great but relies completely on your memory with no prompts. If you learn the methods given on the formula sheet you have something to look at to jog your memory if you go blank on the day. This video teaches this and you can use the worksheet above to practice it.