document.write( "Question 319666: Eighteen points P1, P2, P3, · · · , P18 are equally spaced on a circle. What is the measure of the angle formed by P2P4P8? \n" ); document.write( "

Algebra.Com's Answer #228919 by Edwin McCravy(20060) $\"\"$ $\"About$

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Eighteen points P1, P2, P3, · · · , P18 are equally spaced on a circle. What is the measure of the angle formed by P2P4P8?
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document.write( "We draw the circle and 18 radii to the points P1 to P18. Each of the 18 \r\n" );
document.write( "central angles have a measure of  or 20° each.  \r\n" );
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document.write( "The angle P2P4P8 is an inscribed angle and it is measured by one-half\r\n" );
document.write( "the arc which it intercepts.  That's the big red arc. There are 12 20° \r\n" );
document.write( "central angles subtending the big red arc (count them).\r\n" );
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document.write( "So the measure of the big red arc is 12*20° or 240°. P2P4P8 is the inscribed\r\n" );
document.write( "angle subtending a 240° degree arc.  Since an inscribed angle is measured by \r\n" );
document.write( "one-half of its subtended arc, angle P2P4P8's measure is one-half of\r\n" );
document.write( "240° or 120°\r\n" );
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document.write( "Edwin

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