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Michael McKenna3,451 Points
For those who are not yet math literate, arccos is (1/cos) or the equivalent secant. That is all =)
Balazs Peak46,089 Points
Adam Nettel has the point :D arccos is the inverse function of cos. Sometimes, you want to calculate the cosine of an angle, right? But maybe even more frequently, you want to tell about a number, which angle's cosine it is. Now, THAT is exactly what arccos is used for.
IF the following equation is true: cos( X ) = Y
THEN cos ( Y ) = X
Example: cos ( X ) = 0.5 What is X? Solution: arccos(0.5) = Pi / 3 = 3.14 / 3 (approximately) You can also give the solution in degrees, then it would be 60