math.html

javascript 1.5规范

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<A NAME="1195623"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><BR>
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<zcodeline>y, x
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<ztabletext>Number</ztabletext>
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<zrefheader>Description</zrefheader>
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<A NAME="1195625"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <FONT FACE="courier, couriernew, monospaced size">atan2</FONT> method returns a numeric value between -pi and pi representing the angle theta of an (<FONT FACE="courier, couriernew, monospaced size">x,y</FONT>) point. This is the counterclockwise angle, measured in radians, between the positive X axis, and the point (<FONT FACE="courier, couriernew, monospaced size">x,y</FONT>). Note that the arguments to this function pass the y-coordinate first and the x-coordinate second.</zparagraph>
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<A NAME="1195626"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><FONT FACE="courier, couriernew, monospaced size">atan2</FONT> is passed separate <FONT FACE="courier, couriernew, monospaced size">x</FONT> and <FONT FACE="courier, couriernew, monospaced size">y</FONT> arguments, and <FONT FACE="courier, couriernew, monospaced size">atan</FONT> is passed the ratio of those two arguments.</zparagraph>
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<A NAME="1195627"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Because <FONT FACE="courier, couriernew, monospaced size">atan2</FONT> is a static method of <FONT FACE="courier, couriernew, monospaced size">Math</FONT>, you always use it as <FONT FACE="courier, couriernew, monospaced size">Math.atan2()</FONT>, rather than as a method of a <FONT FACE="courier, couriernew, monospaced size">Math</FONT> object you created.</zparagraph>
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<A NAME="1195629"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following function returns the angle of the polar coordinate:</zparagraph>
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<zcodeline>function getAtan2(x,y) {<br>
&nbsp;&nbsp;&nbsp;return Math.atan2(x,y)<br>
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<A NAME="1195631"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>If you pass <FONT FACE="courier, couriernew, monospaced size">getAtan2</FONT> the values (90,15), it returns 1.4056476493802699; if you pass it the values (15,90), it returns 0.16514867741462683.</zparagraph>
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<A NAME="1195651"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><A HREF="math.html#1195429"  >Math.acos</A>, <A HREF="math.html#1195485"  >Math.asin</A>, <A HREF="math.html#1195541"  >Math.atan</A>, <A HREF="math.html#1195695"  >Math.cos</A>, <A HREF="math.html#1197769"  >Math.sin</A>, <A HREF="math.html#1194346"  >Math.tan</A></zparagraph>
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<A NAME="1195654"> </A>
<A NAME="ceil"> </A>
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<zrefhead2>ceil</zrefhead2>
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<A NAME="1195672"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Returns the smallest integer greater than or equal to a number.<BR>
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<ztabletext><I>Method of</I></ztabletext>
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<A NAME="1195663"> </A>
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<ztabletext><A HREF="math.html#1193138"  >Math</A></ztabletext>
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<A NAME="1195665"> </A>
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<ztabletext><I>Static</I></ztabletext>
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<ztabletext><I>Implemented in</I></ztabletext>
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<A NAME="1195671"> </A>
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<ztabletext>JavaScript 1.0, NES 2.0</ztabletext>
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<ztabletext><I>ECMA version</I></ztabletext>
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<ztabletext>ECMA-262</ztabletext>
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<zrefheader>Syntax</zrefheader>
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<A NAME="1195674"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2">
<zcodeline>ceil(<I>x</I>)
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<A NAME="1195681"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><BR>
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<zcodeline>x
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<ztabletext>A number</ztabletext>
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<A NAME="1195683"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Because <FONT FACE="courier, couriernew, monospaced size">ceil</FONT> is a static method of <FONT FACE="courier, couriernew, monospaced size">Math</FONT>, you always use it as <FONT FACE="courier, couriernew, monospaced size">Math.ceil()</FONT>, rather than as a method of a <FONT FACE="courier, couriernew, monospaced size">Math</FONT> object you created.</zparagraph>
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<A NAME="1195685"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following function returns the ceil value of the variable <FONT FACE="courier, couriernew, monospaced size">x</FONT>:</zparagraph>
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<A NAME="1195686"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2">
<zcodeline>function getCeil(x) {<br>
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<A NAME="1195687"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>If you pass 45.95 to <FONT FACE="courier, couriernew, monospaced size">getCeil</FONT>, it returns 46; if you pass -45.95, it returns -45.</zparagraph>
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<A NAME="1195692"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><A HREF="math.html#1196455"  >Math.floor</A> </zparagraph>
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<A NAME="cos"> </A>
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<zrefhead2>cos</zrefhead2>
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<A NAME="1195713"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Returns the cosine of a number.<BR>
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<ztabletext><I>Method of</I></ztabletext>
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<ztabletext><A HREF="math.html#1193138"  >Math</A></ztabletext>
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<ztabletext><I>Static</I></ztabletext>
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<ztabletext><I>Implemented in</I></ztabletext>
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<A NAME="1195712"> </A>
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<ztabletext>JavaScript 1.0, NES 2.0</ztabletext>
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<ztabletext><I>ECMA version</I></ztabletext>
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<ztabletext>ECMA-262</ztabletext>
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<zrefheader>Syntax</zrefheader>
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<A NAME="1195715"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2">
<zcodeline>cos(<I>x</I>)
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<zrefheader>Parameters</zrefheader>
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<A NAME="1195722"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><BR>
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<zcodeline>x
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<A NAME="1195721"> </A>
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<ztabletext>A number</ztabletext>
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<A NAME="1195724"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The <FONT FACE="courier, couriernew, monospaced size">cos</FONT> method returns a numeric value between -1 and 1, which represents the cosine of the angle.</zparagraph>
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<A NAME="1195725"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Because <FONT FACE="courier, couriernew, monospaced size">cos</FONT> is a static method of <FONT FACE="courier, couriernew, monospaced size">Math</FONT>, you always use it as <FONT FACE="courier, couriernew, monospaced size">Math.cos()</FONT>, rather than as a method of a <FONT FACE="courier, couriernew, monospaced size">Math</FONT> object you created.</zparagraph>
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<A NAME="1195727"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>The following function returns the cosine of the variable <FONT FACE="courier, couriernew, monospaced size">x</FONT>:</zparagraph>
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<A NAME="1195728"></A><FONT FACE="courier, couriernew, monospaced size" SIZE="2">
<zcodeline>function getCos(x) {<br>
&nbsp;&nbsp;&nbsp;return Math.cos(x)<br>
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<A NAME="1195729"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>If <FONT FACE="courier, couriernew, monospaced size">x</FONT> equals 2*<FONT FACE="courier, couriernew, monospaced size">Math.PI</FONT>, <FONT FACE="courier, couriernew, monospaced size">getCos</FONT> returns 1; if <FONT FACE="courier, couriernew, monospaced size">x</FONT> equals <FONT FACE="courier, couriernew, monospaced size">Math.PI</FONT>, the <FONT FACE="courier, couriernew, monospaced size">getCos</FONT> method returns -1.</zparagraph>
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<A NAME="1195746"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph><A HREF="math.html#1195429"  >Math.acos</A>, <A HREF="math.html#1195485"  >Math.asin</A>, <A HREF="math.html#1195541"  >Math.atan</A>, <A HREF="math.html#1195597"  >Math.atan2</A>, <A HREF="math.html#1197769"  >Math.sin</A>, <A HREF="math.html#1194346"  >Math.tan</A></zparagraph>
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<zrefhead2>E</zrefhead2>
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<A NAME="1193381"> </A><FONT FACE="Arial, Helvetica, sans-serif" SIZE="2"><zparagraph>Euler's constant and the base of natural logarithms, approximately 2.718.<BR>
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