Why do sine and cosine NOT have asymptotes, but the other four trig graphs do? Use unit circle ratios to explain?
Sine and cosine do NOT have asymptotes, because their ratios on the unit circle are x (for cosine) and y (for sine), over r. And, r shall always be equal to 1, being the length of the radius of the circle. The logic behind that explaining how they don't have asymptotes, is that for there to be an asymptote, the denominator of a trigonometric function's ratio, has to be able to be equal to 0. Asymptotes only exist when there is a denominator that could possibly be equal to 0, therefore restricting a certain part of the graph. It is from that same requirement for there to be an asymptote, that we can reason that secant/cosecant/tangent/cotangent have asymptotes. Their ratios on the unit circle should be, respectively: r/x. r/y, y/x, and x/y. Since their denominators are not restricted towards being solely 1 as sine and cosine are, 0 is a possibility for the denominators. The end.
