The specification for the trig functions does not specify whether input and output parameters that represent angles are in radians or some other unit.

State that all parameters (both input and output) that represent angles are in radians. This includes at least input arguments to SIN, COS, and TAN, as well as return values from ASIN, ACOS, ATAN and ATAN2. For every return value, specify the range of values (remembering that the inverse trigonometric functions are multi-valued).

Part 4, 3.17.7

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Proposed Disposition of DIS 29500 Comment ECMA-0024 (Modified: 2007-10-17) The unit of arguments and return values that represent angles is the radian. The formulas having such arguments or return values are ACOS, ASIN, ATAN, ATAN2, COS, SIN, and TAN. This will be made explicit in the descriptions of each of these formulas by the addition of the text ", in radians," or ", in radians", as appropriate, as highlighted in the samples below: 3.17.7.50 COS Syntax: COS ( x ) Arguments: Name Type Description x number The value, in radians, whose cosine is to be determined. 3.17.7.4 ACOS Syntax: ACOS ( x ) Return Type and Value: number ­ The arc cosine of x , in radians . Similar Comments: AU-0025 , CA-0048 , CL-0017 , CL-0018 , CL-0019 , CL-0020 , CL-0021 , CL-0022 , CL-0023 , CL-0159 , CL-0166 , CL-0178 , CL-0182 , CO-0159 , CO-0162 , CO-0163 , CO-0164 , CO-0174 , CO-0201 , CO-0202 , DK-0161 , FR-0440 , FR-0444 , FR-0445 , FR-0446 , FR-0482 , FR-0490 , FR-0505 , GB-0371 , GB-0374 , GB-0375 , GB-0376 , GB-0386 , GB-0424 , GB-0431 , GR-0103 , IE-0007 , IN-0073 , PH-0002 , US-0173 , US-0176 , US-0177 , US-0178 , US-0185 , US-0220 , US-0227 , UY-0009