usr/src/lib/libm/common/complex/ctan.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 /*
  26  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29
  30 #pragma weak __ctan = ctan
  31
  32 /* INDENT OFF */
  33 /*
  34  * dcomplex ctan(dcomplex z);
  35  *
  36  * If z = x+iy, then since ctan(iz) = i*ctanh(z),  we have
  37  *
  38  * ctan(z)      = ctan((-1)*(-z)) = ctan(i*i*(-z))
  39  *              = i*ctanh(i*(-z)) = i*ctanh(i*(-x-yi))
  40  *              = i*ctanh(y-ix)
  41  *              = -Im(ctanh(y-ix))+i*Re(ctanh(y-ix))
  42  */
  43 /* INDENT ON */
  44
  45 #include "libm.h"
  46 #include "complex_wrapper.h"
  47
  48 dcomplex
  49 ctan(dcomplex z) {
  50         double x, y;
  51         dcomplex ans, ct;
  52
  53         x = D_RE(z);
  54         y = D_IM(z);
  55         D_RE(z) = y;
  56         D_IM(z) = -x;
  57         ct = ctanh(z);
  58         D_RE(ans) = -D_IM(ct);
  59         D_IM(ans) = D_RE(ct);
  60         return (ans);
  61 }