cos(-x)
cosx
The function cos(-x) means cosine of the negative of x. In other words, we evaluate the cosine function for the opposite angle of x on the unit circle.
The cosine function is an even function, which means that cos(-x) = cos(x) for all values of x. This property is a result of the geometric definition of cosine on the unit circle, where the cosine of an angle is the x-coordinate of the point where the angle intercepts the unit circle.
Therefore, to find cos(-x), we simply evaluate the cosine of x. For example, if x = π/4, then cos(-x) = cos(-π/4) = cos(π/4) = √2/2.
In summary, cos(-x) is equal to cos(x) because cosine is an even function.
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