Input to the arc-cosine function must be between -1 and 1, inclusive.
For example, given a ratio of 0.5, the function returns an angle of 1.047 radians.
ACOS is the inverse of the COS function.
To supply an angle to COS in degrees, use the RADIANS function to convert to radians.
ASIN Function
The Excel ASIN function returns the inverse sine of a number.
ATAN Function
The Excel ATAN function returns the inverse tangent of a number.
The function is the inverse of TAN.
