It is not indicated whether the parameter is in radians or degrees
Specify the angular units that this parameter is in
page 2798, line 1 Part 4, Section 3.17.7.313 TAN
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Proposed Disposition of DIS 29500 Comment FR-0490 (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 , ECMA-0024 , FR-0440 , FR- 0444 , FR-0445 , FR-0446 , FR-0482 , 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

Dupe of Ecma 24