A useful resource for all high school students, I made a ‘cheatsheet’ (don’t worry, it doesn’t fall under ‘unfair means’, it’s just term) for trigionometric ratios, including two angles, double angles, half angles, triple angles, and conditional identities in a triangle. You can download this PDF file from this place, and then use it as a handy reference while solving problems. Hopfully, you’ll need this only initially, and with more practice, you’ll be able to solve those easy-peasy math questions on trigonometric ratios yourself.
So here you go, download the file.
Note: There’s an old (and better-looking) version of the cheatsheet too, which you can download from here, but it has a mistake; at one point, instead of ‘tan2 (A / 2)’ it should be ‘tan^2 (A / 2). Also, the old one was on three pages; the new one’s in a compact two-page form.