cos(-x)
cosx
The cos function is an even function, which means that cos(-x) is equal to cos(x). In other words, the cosine of the opposite of an angle is equal to the cosine of that angle.
To illustrate this, let’s assume x is 45 degrees. Then:
cos(-x) = cos(-(45)) = cos(-45)
Using the cosine of difference formula:
cos(-45) = cos(0 – 45) = cos(0)cos(45) + sin(0)sin(45)
Since cos(0) = 1 and sin(0) = 0, this simplifies to:
cos(-45) = cos(45) = √2/2
Therefore, cos(-x) is equal to cos(x), or in this example, cos(-45) = cos(45) = √2/2.
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