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<!DOCTYPE html>
<html data-require="math graphie graphie-helpers angles">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Corresponding angles</title>
<script src="../khan-exercise.js"></script>
</head>
<body>
<div class="exercise">
<div class="vars">
<var id="ANCHOR">randRange( 20, 160 )</var>
<var id="KNOWN_INDEX">randRange( 0, 7 )</var>
<var id="UNKNOWN_INDEX">( KNOWN_INDEX + 4 ) % 8</var>
<var id="MEASURE">KNOWN_INDEX % 2 === 0 ? ANCHOR : 180 - ANCHOR</var>
</div>
<div class="problems">
<div>
<p>The two horizontal lines are parallel, and there is a third line that intersects them as shown below.</p>
<p class="question">If we know that the <span class="hint_blue">blue angle is <var>MEASURE</var> degrees</span>, what is the <span class="hint_orange">measure of the orange angle</span>?</p>
<p class="solution" data-forms="integer"><var>MEASURE</var></p>
<div class="graphie" id="parallel-lines">
init({
range: [ [ -1, 11 ], [-1, 4] ]
});
graph.pl = new ParallelLines( 0, 0, 10, 0, 3 );
graph.pl.draw();
graph.pl.drawMarkers(ANCHOR);
graph.pl.drawTransverse( ANCHOR );
graph.pl.drawAngle( KNOWN_INDEX, true );
graph.pl.drawAngle( UNKNOWN_INDEX, false, "#FFA500" );
</div>
</div>
</div>
<div class="hints">
<p>Notice that the blue and orange angles are in the same position but at different intersections.</p>
<p>One way to describe the angles is to say that they are corresponding angles.</p>
<p>There is a proof for why corresponding angles are equal, but for now let's just take that on faith.</p>
<div>
<p>The orange angle measures <var>MEASURE</var> degrees.</p>
<div class="graphie" data-update="parallel-lines">
graph.pl.drawAngle( UNKNOWN_INDEX, true, "#FFA500" );
</div>
</div>
</div>
</div>
</body>
</html>
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