The diameter of the circle is not specified, just explain it. D is usually used, and the distance between two quantities doesn't have to be set to d ... whatever you want, but explain the mathematical meaning of "proportion" generally means y=kx, and one is called positive correlation, so don't confuse it. "Two sides of Angle A" means that the two sides forming Angle A are adjacent and opposite, which has the same meaning as being isolated and opposite. Is it an added function? One plus one minus is a minus function, right? Composite functions can be said that, but it's hard to say without composite.