What are Trigonometric Ratios?

The ratios depend only on the angle, not on the size of the triangle. $\tan\theta = \dfrac{\sin\theta}{\cos\theta}$, and $\sin^2\theta + \cos^2\theta = 1$. As an angle approaches $90^\circ$, $\tan\theta$ becomes very large, because the adjacent side becomes very small: $\tan 89.9^\circ \approx 573$. At exactly $90^\circ$, $\tan\theta$ is not defined. Remember the values at $30^\circ$, $45^\circ$ and $60^\circ$.