cosh.c revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8
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25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Copyright 2005 Sun Microsystems, Inc. All rights reserved.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Use is subject to license terms.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis/* INDENT OFF */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Code originated from 4.3bsd.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Modified by K.C. Ng for SUN 4.0 libm.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 1. Replace x by |x| (cosh(x) = cosh(-x)).
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * [ exp(x) - 1 ]^2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 0 <= x <= 0.3465 : cosh(x) := 1 + -------------------
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * exp(x) + 1/exp(x)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 0.3465 <= x <= 22 : cosh(x) := -------------------
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * 22 <= x <= lnovft : cosh(x) := exp(x)/2
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * lnovft <= x < INF : cosh(x) := scalbn(exp(x-1024*ln2),1023)
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Note: .3465 is a number near one half of ln2.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * Special cases:
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * cosh(x) is |x| if x is +INF, -INF, or NaN.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis * only cosh(0)=1 is exact for finite x.
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis/* INDENT ON */
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtisstatic const double
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis return (w * w);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis if (w < 0.3465) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis w = 1.0 + (t * t) / (w + w);
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if (w < 22.0) {
25c28e83beb90e7c80452a7c818c5e6f73a07dc8Piotr Jasiukajtis } else if (w <= lnovft) {