A name server is a computer hardware or software server that implements a network service for providing responses to queries against a directory service.It translates an often humanly-meaningful, text-based identifier to a system-internal, often numeric identification or addressing component. name server indicates that its response is authoritative by setting the Authoritative Answer (AA) bit in the response to a query on a name for which it is authoritative. Name servers providing answers for which they are not authoritative (for example, name servers for parent zones) do not set the AA bit.
Trigonometry (from Greek trigÅnon, triangle and metron, measure) is a branch of mathematics that studies relationships involving lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies.
Inverse Trigonometric Functions. The inverse trigonometric functions are the inverse functions of the trigonometric functions, written , , , , , and . Alternate notations are sometimes used, as summarized in the following table.