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<h1 id="firstHeading" class="firstHeading">asin, asinf, asinl</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><math.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">float asinf( float arg );</pre>
</td> <td> (1) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> <tr class="t-dcl"> <td> <pre data-language="c">double asin( double arg );</pre>
</td> <td> (2) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">long double asinl( long double arg );</pre>
</td> <td> (3) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> <tr class="t-dcl t-since-c23"> <td> <pre data-language="c">_Decimal32 asind32( _Decimal32 arg );</pre>
</td> <td> (4) </td> <td> <span class="t-mark-rev t-since-c23">(since C23)</span> </td> </tr> <tr class="t-dcl t-since-c23"> <td> <pre data-language="c">_Decimal64 asind64( _Decimal64 arg );</pre>
</td> <td> (5) </td> <td> <span class="t-mark-rev t-since-c23">(since C23)</span> </td> </tr> <tr class="t-dcl t-since-c23"> <td> <pre data-language="c">_Decimal128 asind128( _Decimal128 arg );</pre>
</td> <td> (6) </td> <td> <span class="t-mark-rev t-since-c23">(since C23)</span> </td> </tr> <tr class="t-dsc-header"> <th> Defined in header <code><tgmath.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">#define asin( arg )</pre>
</td> <td> (7) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> </table> <div class="t-li1">
<span class="t-li">1-6)</span> Computes the principal values of the arc sine of <code>arg</code>.</div> <div class="t-li1">
<span class="t-li">7)</span> Type-generic macro: If the argument has type <code>long double</code>, <span class="t-v">(3)</span> (<code>asinl</code>) is called. Otherwise, if the argument has integer type or the type <code>double</code>, <span class="t-v">(2)</span> (<code>asin</code>) is called. Otherwise, <span class="t-v">(1)</span> (<code>asinf</code>) is called. If the argument is complex, then the macro invokes the corresponding complex function (<code><a href="../complex/casin" title="c/numeric/complex/casin">casinf</a></code>, <code><a href="../complex/casin" title="c/numeric/complex/casin">casin</a></code>, <code><a href="../complex/casin" title="c/numeric/complex/casin">casinl</a></code>).</div> <table class="t-rev-begin"> <tr class="t-rev t-since-c23">
<td> <p>The functions <span class="t-v">(4-6)</span> are declared if and only if the implementation predefines <code>__STDC_IEC_60559_DFP__</code> (i.e. the implementation supports decimal floating-point numbers).</p>
</td> <td><span class="t-mark-rev t-since-c23">(since C23)</span></td>
</tr> </table> <h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> arg </td> <td> - </td> <td> floating-point value </td>
</tr>
</table> <h3 id="Return_value"> Return value</h3> If no errors occur, the arc sine of <code>arg</code> (arcsin(arg)) in the range [-<span><span>π</span><span>/</span><span>2</span></span> ; +<span><span>π</span><span>/</span><span>2</span></span>], is returned. <p>If a domain error occurs, an implementation-defined value is returned (NaN where supported).</p>
<p>If a range error occurs due to underflow, the correct result (after rounding) is returned.</p>
<h3 id="Error_handling"> Error handling</h3> <p>Errors are reported as specified in <a href="math_errhandling" title="c/numeric/math/math errhandling"><code>math_errhandling</code></a>.</p>
<p>Domain error occurs if <code>arg</code> is outside the range <code>[-1.0; 1.0]</code>.</p>
<p>If the implementation supports IEEE floating-point arithmetic (IEC 60559):</p>
<ul>
<li> if the argument is ±0, it is returned unmodified; </li>
<li> if |arg| > 1, a domain error occurs and NaN is returned; </li>
<li> if the argument is NaN, NaN is returned. </li>
</ul> <h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include <errno.h>
#include <fenv.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
#ifndef __GNUC__
#pragma STDC FENV_ACCESS ON
#endif
int main(void)
{
printf("asin( 1.0) = %+f, 2*asin( 1.0)=%+f\n", asin(1), 2 * asin(1));
printf("asin(-0.5) = %+f, 6*asin(-0.5)=%+f\n", asin(-0.5), 6 * asin(-0.5));
// special values
printf("asin(0.0) = %1f, asin(-0.0)=%f\n", asin(+0.0), asin(-0.0));
// error handling
errno = 0; feclearexcept(FE_ALL_EXCEPT);
printf("asin(1.1) = %f\n", asin(1.1));
if (errno == EDOM)
perror(" errno == EDOM");
if (fetestexcept(FE_INVALID))
puts(" FE_INVALID raised");
}</pre></div> <p>Possible output:</p>
<div class="text source-text"><pre data-language="c">asin( 1.0) = +1.570796, 2*asin( 1.0)=+3.141593
asin(-0.5) = -0.523599, 6*asin(-0.5)=-3.141593
asin(0.0) = 0.000000, asin(-0.0)=-0.000000
asin(1.1) = nan
errno == EDOM: Numerical argument out of domain
FE_INVALID raised</pre></div> </div> <h3 id="References"> References</h3> <ul>
<li> C23 standard (ISO/IEC 9899:2023): </li>
<ul>
<li> 7.12.4.2 The asin functions (p: TBD) </li>
<li> 7.25 Type-generic math <tgmath.h> (p: TBD) </li>
<li> F.10.1.2 The asin functions (p: TBD) </li>
</ul>
<li> C17 standard (ISO/IEC 9899:2018): </li>
<ul>
<li> 7.12.4.2 The asin functions (p: 174) </li>
<li> 7.25 Type-generic math <tgmath.h> (p: 272-273) </li>
<li> F.10.1.2 The asin functions (p: 378) </li>
</ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul>
<li> 7.12.4.2 The asin functions (p: 238) </li>
<li> 7.25 Type-generic math <tgmath.h> (p: 373-375) </li>
<li> F.10.1.2 The asin functions (p: 518) </li>
</ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul>
<li> 7.12.4.2 The asin functions (p: 219) </li>
<li> 7.22 Type-generic math <tgmath.h> (p: 335-337) </li>
<li> F.9.1.2 The asin functions (p: 456) </li>
</ul>
<li> C89/C90 standard (ISO/IEC 9899:1990): </li>
<ul><li> 4.5.2.2 The asin function </li></ul>
</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="acos" title="c/numeric/math/acos"> <span class="t-lines"><span>acos</span><span>acosf</span><span>acosl</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes arc cosine (\({\small\arccos{x} }\)arccos(x)) <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="atan" title="c/numeric/math/atan"> <span class="t-lines"><span>atan</span><span>atanf</span><span>atanl</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes arc tangent (\({\small\arctan{x} }\)arctan(x)) <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="atan2" title="c/numeric/math/atan2"> <span class="t-lines"><span>atan2</span><span>atan2f</span><span>atan2l</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes arc tangent, using signs to determine quadrants <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="sin" title="c/numeric/math/sin"> <span class="t-lines"><span>sin</span><span>sinf</span><span>sinl</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes sine (\({\small\sin{x} }\)sin(x)) <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="../complex/casin" title="c/numeric/complex/casin"> <span class="t-lines"><span>casin</span><span>casinf</span><span>casinl</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes the complex arc sine <br> <span class="t-mark">(function)</span> </td>
</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/numeric/math/asin" title="cpp/numeric/math/asin">C++ documentation</a></span> for <code>asin</code> </td>
</tr> </table> <div class="_attribution">
<p class="_attribution-p">
© cppreference.com<br>Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.<br>
<a href="https://en.cppreference.com/w/c/numeric/math/asin" class="_attribution-link">https://en.cppreference.com/w/c/numeric/math/asin</a>
</p>
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