Cos

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Returns the cosine of $arg

namespace HH\Lib\Math;

function cos(
  num $arg,
): float;

• To find the sine, see Math\sin().
• To find the tangent, see Math\tan().

Parameters

• num $arg

Returns

• float