document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=61248>Question 61248</A>This question is from textbook <A HREF=http://www.amazon.com/exec/obidos/ASIN/0030522196/algebrahomeworkh></A><BR>\n" );
document.write( ": <I><SPAN STYLE=\"word-break: break-all;\"> Here's the question from the book:\"An interior angle of a regular polygon is given. Find the number of sides of the polygon.<BR>\n" );
document.write( " How do you find the number of sides? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #42143 by </B><A HREF=/tutors/aboutme.mpl?userid=joyofmath><B>joyofmath(189)</B></A><img src=\"/images/stars/stars-09.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=joyofmath><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=42143\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Here's the question from the book:\"An interior angle of a regular polygon is given. Find the number of sides of the polygon.\r<BR>\n" );
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document.write( "A regular polygon has all sides the same and also all interior angles are the same.\r<BR>\n" );
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document.write( "A regular triangle has 3 internal angles that add up to 180 degrees.<BR>\n" );
document.write( "A regular square has 4 internal angles that add up to 360 degrees.<BR>\n" );
document.write( "A regular pentagon has 5 internal angles that add up to 540 degrees.\r<BR>\n" );
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document.write( "Every time you add a side to a polygon you add 180 degrees.\r<BR>\n" );
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document.write( "So, a 3-sided polygon has 1*180 degrees.<BR>\n" );
document.write( "A 4-sided polygon has 2*180 degrees.<BR>\n" );
document.write( "A 5-sided polygon has 3*180 degrees.\r<BR>\n" );
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document.write( "In general, an n-sided polygon has <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28n-2%29%2A180+degrees ALIGN=MIDDLE  ALT=\"%28n-2%29%2A180+degrees\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "The interior angle of a regular n-sided polygon, call it I = <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28%28n-2%29%2A180%29%2Fn ALIGN=MIDDLE  ALT=\"%28%28n-2%29%2A180%29%2Fn\"   DISABLED_style= \"max-width:90%; height:auto;\" >.\r<BR>\n" );
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document.write( "So, if you know I and want to solve for n, you do the following algebra:\r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=I=%28%28n-2%29%2A180%29%2Fn ALIGN=MIDDLE  ALT=\"I=%28%28n-2%29%2A180%29%2Fn\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "Multiply by n: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=In=%28n-2%29%2A180%29 ALIGN=MIDDLE  ALT=\"In=%28n-2%29%2A180%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "Or, <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=In=180n-360 ALIGN=MIDDLE  ALT=\"In=180n-360\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "Subtract 180n from both sides: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=In-180n=-360 ALIGN=MIDDLE  ALT=\"In-180n=-360\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "Factor out n: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n%28I-180%29=-360 ALIGN=MIDDLE  ALT=\"n%28I-180%29=-360\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Divide by I-180: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n=-360%2F%28I-180%29 ALIGN=MIDDLE  ALT=\"n=-360%2F%28I-180%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.<BR>\n" );
document.write( "Multiply numerator and denominator by -1: <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n=360%2F%28180-I%29 ALIGN=MIDDLE  ALT=\"n=360%2F%28180-I%29\"   DISABLED_style= \"max-width:90%; height:auto;\" >.\r<BR>\n" );
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document.write( "Verify the equation:\r<BR>\n" );
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document.write( "If I = 60 then <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n=360%2F%28180-60%29+=+360%2F120+=+3 ALIGN=MIDDLE  ALT=\"n=360%2F%28180-60%29+=+360%2F120+=+3\"   DISABLED_style= \"max-width:90%; height:auto;\" > A triangle!<BR>\n" );
document.write( "If I = 90 then <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n=360%2F%28180-90%29+=+360%2F90+=+4 ALIGN=MIDDLE  ALT=\"n=360%2F%28180-90%29+=+360%2F90+=+4\"   DISABLED_style= \"max-width:90%; height:auto;\" > A square!<BR>\n" );
document.write( "If I = 108 then <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=n=360%2F%28180-108%29+=+360%2F72+=+5 ALIGN=MIDDLE  ALT=\"n=360%2F%28180-108%29+=+360%2F72+=+5\"   DISABLED_style= \"max-width:90%; height:auto;\" > A pentagon! </SPAN>\n" );
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