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Section: Mathematical Functions
Computes the acos function for its argument. The general syntax for its use is 
y = acos(x)
 where x is an n-dimensional array of numerical type. Integer types are promoted to the double type prior to calculation of the acos function. Output y is of the same size and type as the input x, (unless x is an integer, in which case y is a double type). 
Mathematically, the acos function is defined for all arguments x as 
![\[ \mathrm{acos} x \equiv \frac{pi}{2} + i \log \left(i x + \sqrt{1-x^2}\right). \]](form_39.png) 
 For real valued variables x in the range [-1,1], the function is computed directly using the standard C library's numerical acos function. For both real and complex arguments x, note that generally 
![\[ \mathrm{acos}(\cos(x)) \neq x, \]](form_40.png) 
The following code demonstates the acos function over the range [-1,1].
--> t = linspace(-1,1); --> plot(t,acos(t))
