Trig Ratios: There are 6 trig ratios(3 basic and 3 reciprocal) that can be used when evaluating a triangle.
3 basic: Sinx=y/R, Cosx=x/R, Tanx=y/x
3 Reciprocal(the 3 basic flipped to cosecant, secant, and cotangent): cscx=R/y, secx=R/x, cotx=x/y
*y is the side of the triangle opposite of the angle being considered, x is adjacent to the angle and R is the hypotenuse.
Also take into consideration where sin, cos, and tan are positive and where they are negative on the Cartesian plane. In Quadrant I, all 3 ratios are positive. In QII, only Sine is positive, in QIII, only tan is positive, and in QIV, only cosine is positive.
This information can be applied to problems where you have to find the angle theta given a point on the unit circle. The point would give you the x and y values and you can find R(hypotenuse) by using Pythagoras theorem--> x^2+y^2=R^2(or if the triangle is on the unit circle, R will always be 1). When x, y , and R values are calculated, the 6 trig ratios can be evaluated and angle theta can be found using one of them. The location on the Cartesian plane of the points can be determined by looking at the x,y values(whether they are negative or positive).