Is sin the X or Y?
Similarly, is y sin over X?
The point of the unit circle is that it makes other parts of the mathematics easier and neater. For instance, in the unit circle, for any angle θ, the trig values for sine and cosine are clearly nothing more than sin(θ) = y and cos(θ) = x.
Considering this, is Tan the X or Y?
The unit circle definition is tan(theta)=y/x or tan(theta)=sin(theta)/cos(theta). The tangent function is negative whenever sine or cosine, but not both, are negative: the second and fourth quadrants. Tangent is also equal to the slope of the terminal side. We talked about the sine and cosine functions.
The horizontal is sin and the vertical cos because they have given the angle to the vertical in this question, not the angle to the horizontal as in the earlier examples.