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 /*
  27  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 #pragma weak __ctan = ctan
  32 
  33 
  34 /*
  35  * dcomplex ctan(dcomplex z);
  36  *
  37  * If z = x+iy, then since ctan(iz) = i*ctanh(z),  we have
  38  *
  39  * ctan(z)      = ctan((-1)*(-z)) = ctan(i*i*(-z))
  40  *              = i*ctanh(i*(-z)) = i*ctanh(i*(-x-yi))
  41  *              = i*ctanh(y-ix)
  42  *              = -Im(ctanh(y-ix))+i*Re(ctanh(y-ix))
  43  */
  44 
  45 #include "libm.h"
  46 #include "complex_wrapper.h"
  47 
  48 dcomplex
  49 ctan(dcomplex z)
  50 {
  51         double x, y;
  52         dcomplex ans, ct;
  53 
  54         x = D_RE(z);
  55         y = D_IM(z);
  56         D_RE(z) = y;
  57         D_IM(z) = -x;
  58         ct = ctanh(z);
  59         D_RE(ans) = -D_IM(ct);
  60         D_IM(ans) = D_RE(ct);
  61         return (ans);
  62 }