L4 Limits at Infinity - Part 1
Completion requirements
Unit 1B
Limits
Lesson 4: Limits at Infinity
According to the Big Bang Theory, the universe began in a colossal explosion roughly «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mn»13«/mn»«mo».«/mo»«mn»7«/mn»«/mrow»«/mstyle»«/math»
billion years ago. Ever since that moment, the universe has been expanding. Astronomers are currently studying what the future expansion of the universe will look like. One of the many possibilities is that the universe will expand forever. In an
odd sort of paradox, one expansion possibility is that the universe expands forever, but eventually reaches a maximum size. While this might seem like a contradiction, combining the concepts of limits with the idea of infinity enables scientists to
slowly piece together the future of the entire cosmos!
Just as when studying the future of the universe, when graphing functions, it is important to understand what happens to the graph as «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»x«/mi»«/mstyle»«/math» increases «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfenced»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mo»+«/mo»«mo»§#8734;«/mo»«/mrow»«/mfenced»«/mstyle»«/math» or decreases «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfenced»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mo»§#8722;«/mo»«mo»§#8734;«/mo»«/mrow»«/mfenced»«/mstyle»«/math» without bound. To begin to understand this end behaviour of functions, consider the function «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mfrac»«mrow»«msup»«mi»x«/mi»«mn»2«/mn»«/msup»«mo»§#8722;«/mo»«mn»1«/mn»«/mrow»«mrow»«msup»«mi»x«/mi»«mn»2«/mn»«/msup»«mo»+«/mo»«mn»1«/mn»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math», graphed below.
Just as when studying the future of the universe, when graphing functions, it is important to understand what happens to the graph as «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»x«/mi»«/mstyle»«/math» increases «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfenced»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mo»+«/mo»«mo»§#8734;«/mo»«/mrow»«/mfenced»«/mstyle»«/math» or decreases «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mfenced»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mo»§#8722;«/mo»«mo»§#8734;«/mo»«/mrow»«/mfenced»«/mstyle»«/math» without bound. To begin to understand this end behaviour of functions, consider the function «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mfrac»«mrow»«msup»«mi»x«/mi»«mn»2«/mn»«/msup»«mo»§#8722;«/mo»«mn»1«/mn»«/mrow»«mrow»«msup»«mi»x«/mi»«mn»2«/mn»«/msup»«mo»+«/mo»«mn»1«/mn»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math», graphed below.
It appears the value of the function gets closer and closer to «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mn»1«/mn»«/mstyle»«/math» as the «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»x«/mi»«/mstyle»«/math»-value increases and decreases towards positive and negative infinity, respectively. The graph below shows the same function with a different scale along the «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»x«/mi»«/mstyle»«/math»-axis.
The dotted line on the graph below indicates the horizontal asymptote.
