arc-hyperbolic cosine[‚ärk ‚hī·pər‚bäl·ik ′kō‚sīn]
Also known as inverse hyperbolic cosine.
For a number, x, equal to or greater than 1, either of the two numbers whose hyperbolic cosine equals x.
For a number, x, equal to or greater than 1, the positive number whose hyperbolic cosine equals x ; it is the value at x of the restriction of the inverse of the hyperbolic cosine function to the positive numbers.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.