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    <p>Let's do the math for a second.</p> <ul> <li>The first line is <code>(0, 61.632653061218946)-(944, 217.25510204080692)</code>. Slope is <code>rise/run</code>, therefore <code>m = 0.16485428917329234533898305084746</code>.</li> <li>The second line is <code>(0, 61.632653061218946)-(9440, 2172.5510204080692)</code>; <code>m = 0.22361423382911549300847457627119</code>.</li> </ul> <p><em>The slopes are different, which is just another way of saying the angles are different.</em></p> <p>What you need to do is <em>extend</em> the line. You cannot just multiply both coordinates of one of the points by 10. First determine either an x or a y beyond the bounds of your canvas, then <em>solve for the other value</em>. </p> <p>How do you do this?</p> <ol> <li><p>First, get the equation for the line. A line is defined by <code>y=m*x+b</code>, where <code>m</code> is the slope, and <code>b</code> is the y-intercept. </p> <ol> <li>We already know how to calculate the slope (<code>rise/run</code> = <code>y2 - y1 / x2 - x1</code>). We get <code>0.16485428917329234533898305084746</code></li> <li>Plug in the slope and solve for <code>b</code> (<code>y - m*x</code>), you get <code>61.632653061218946</code>. In your case you already have this value as the y-intercept is the y-coordinate when <code>x=0</code>.</li> <li>You then get the equation <code>y = 0.16485428917329234533898305084746 * x + 61.632653061218946</code></li> </ol></li> <li><p>Now, pick a sufficiently large x, say 10000. Plug this value in and solve for y. You get <code>1710.1755447941423993898305084746</code>.</p></li> <li><p>Finally, draw your line to this new point, <code>(0, 61.632653061218946)-(10000,1710.1755447941423993898305084746)</code></p></li> </ol> <p>Great, now let's generalize this.</p> <ul> <li>We have two points <code>(x1, y1)</code> and <code>(x2, y2)</code>. We want to solve for <code>(10000, y3)</code>.</li> <li>Therefore, <code>y3 = m*x3 + b</code>, or <code>y3 = m * 10000 + b</code>.</li> <li>We also know that <code>b = y - m * x</code>, so plugging this in and arbitrarily choosing point 1, <code>y3 = m * 10000 + y1 - m * x1</code>.</li> <li>Ok, let's factor out the <code>m</code>: <code>y3 = m * (10000 + x1) - y1</code>.</li> <li>We know <code>m = (y2 - y1) / (x2 - x1)</code>, so plugging this in: <code>y3 = ((y2 - y1) / (x2 - x1)) * (10000 + x1) - y1</code>.</li> </ul> <p>If your line doesn't start at <code>x = 0</code>, you will need to repeat this process for <code>x = 0</code>, meaning you should plot a line <code>(0, ((y2 - y1) / (x2 - x1)) * x1 - y1)-(10000,((y2 - y1) / (x2 - x1)) * (10000 + x1) - y1)</code>.</p> <p>Note: If <code>x2 - x1</code> is 0, you have an infinite slope. This is a vertical line, and you'll have to handle this case separately.</p>
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    1. PODraw an infinite line through 2 points?
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    1. COWatch out for extreme slopes, since you're dealing with floating point values. Especially, when the slope is infinity you have a problem.
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    2. CO+1 for getting the correct answer first and correcting my answer.
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    3. COThank you for your extensive reply, i had to read it multiple times to fully understand, but that is because i'm not very good at math and algo. But your explanation makes even sense to me.
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