The expression cos(2θ) refers to the cosine of double the angle θ and is a crucial part of the study of trigonometric identities. It showcases how angles can be transformed and provides multiple equivalent forms for cos(2θ) based on fundamental trigonometric identities, enabling simplification and solving of various equations. Understanding cos(2θ) not only aids in simplifying expressions but also connects with concepts of periodic functions and the behavior of the cosine function.
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