Geometry Level 3

How many of the following functions are not sinusoidal?

• $$f(x) = \dfrac{x}{\sin x}$$
• $$f(x) = \dfrac{\cos x}{\sin x}$$
• $$f(x) = \dfrac{\sin x}{\sec 180^\circ}$$

Definition: A sinusoidal function is continuous and periodic.

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