## Trigonometry (11th Edition) Clone

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Recall: (1) An angle and its reference angle either have the same trigonometric function values or differ only in signs. (2) $\tan{\theta}=\dfrac{y}{x}$ $\pi$ is a special angle whose terminal side is the negative x-axis. The negative x-axis intercepts the unit circle at the point $(-1, 0)$. Therefore, $\tan{\pi} = \dfrac{0}{-1} = 0$