Find the matching value for f

Question

Find the matching value for f in the function below. The independent variable is in radians.

 

ƒ(π/4) = cos(cos^-1x)

Answer 1

The cosine of arccosine(x)  (or cos^-1(x) )  returns  x  for  -1 ≤ x ≤ 1. Since pi/4 is between -1 and 1, f(pi/4) returns pi/4.

 

See http://www.rapidtables.com/math/trigonometry/arccos.htm