Question

what does cos(cos X) mean?

Answer 1

The cosine function, along with sine and tangent, is one of the three most common trigonometric functions. In any right triangle, the cosine of an angle is the length of the adjacent side (A) divided by the length of the hypotenuse (H). In a formula, it iswritten simply as 'cos'.

Answer 2

cos cos x =cos{1/2(e^ix+e^-ix)}