Trigonometry is the study of triangles, specifically right triangles, specifically the angles and side of right triangles. It is also a long word that I still don’t know the root of.
Trigonometry deals with the ratios of sine (sin), cosine (cos), and tangent (tan). The shortened versions (as seen in the brackets) can be found on a calculator, and you can figure out angle degrees using them.
Sine is equal to opposite/hypotenuse. Cosine is equal to adjacent/hypotenuse. Tangent is equal to opposite/adjacent.
Opposite and adjacent sides are in comparison to the angle you’re working with, most likely “x”. “X” can never be a right angle, because then the opposite is the hypotenuse, and that just does not work.
There are also a series of right triangles where you don’t need a calculator to figure out the ratio, such as when the adjacent and opposite both equal 1, and hypotenuse is √2.
Sine, cosine, and tangent, you put in an angle and that gives you ratio. The inverse operations (ex. sin-1), you need to put in the ratio and it will give you the angle. Both ways will help you find the required sign or the angle.