L3 Limit Properties - Part 1
Completion requirements
Unit 1B
Limits
Lesson 3: Limit Properties
In the English language, there are rules about the sentence structure, active versus passive voice, and when to use a verb instead of an adverb, to name a few. Every language has similar rules that govern the meaning of words and how those words can
be used. Mathematics is no different; many math rules are called theorems. Theorems give formal structure to the discipline and help ensure the foundations of areas of study like calculus are rigorously proven.
In previous courses, you used the Pythagorean theorem to calculate the leg lengths or the hypotenuse of a right triangle.
In this Lesson, eight limit properties will be introduced and used to evaluate some complicated limits.
Although the proofs of the properties are beyond the scope of this course, trust they provide firm evidence of their validity, or better yet, use a search engine to search for the individual proofs yourself.
In previous courses, you used the Pythagorean theorem to calculate the leg lengths or the hypotenuse of a right triangle.
In this Lesson, eight limit properties will be introduced and used to evaluate some complicated limits.
Although the proofs of the properties are beyond the scope of this course, trust they provide firm evidence of their validity, or better yet, use a search engine to search for the individual proofs yourself.
The video, The Properties of Limits, below will introduce you to most of the limit theorems you need to know in Math 31.
Note: In the video, the narrator uses the phrase goes to. The proper terminology for this is approaches.
The properties presented in the video are summarized in the box below.
Note: In the video, the narrator uses the phrase goes to. The proper terminology for this is approaches.
The properties presented in the video are summarized in the box below.
Suppose the limits
both exist, where «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»c«/mi»«/mstyle»«/math» is a constant. Then, it follows that:
Property 1 – The limit of a sum is the sum of the limits.
Property 2 – The limit of a difference is the difference of the limits.
Property 3 – The limit of a product is the product of the limits.
Property 4 –The limit of a quotient is the quotient of the limits.
Property 5 – The limit of a constant is the constant.
Property 6 – The limit of a constant multiplied by a function is the constant multiplied by the limit of the function.
Property 7 – The limit of a power is the power of the limit.
Property 8 – The limit of a root is the root of the limit.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi
mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math» and «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»g«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math»
both exist, where «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»c«/mi»«/mstyle»«/math» is a constant. Then, it follows that:
Property 1 – The limit of a sum is the sum of the limits.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mfenced open=¨[¨ close=¨]¨»«mrow»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi
mathvariant=¨normal¨»)«/mi»«mo»+«/mo»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mfenced»«mo»=«/mo»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»+«/mo»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math»
Property 2 – The limit of a difference is the difference of the limits.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mfenced open=¨[¨ close=¨]¨»«mrow»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi
mathvariant=¨normal¨»)«/mi»«mo»§#8722;«/mo»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mfenced»«mo»=«/mo»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»§#8722;«/mo»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math»
Property 3 – The limit of a product is the product of the limits.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mfenced open=¨[¨ close=¨]¨»«mrow»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi
mathvariant=¨normal¨»)«/mi»«mo»§#8729;«/mo»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mfenced»«mo»=«/mo»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»§#8729;«/mo»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math»
Property 4 –The limit of a quotient is the quotient of the limits.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mfrac»«mrow»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi
mathvariant=¨normal¨»)«/mi»«/mrow»«mrow»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mfrac»«mo»=«/mo»«mfrac»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math»,
where «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi
mathvariant=¨normal¨»)«/mi»«mo»§#8800;«/mo»«mn»0«/mn»«/mrow»«/mstyle»«/math»
Property 5 – The limit of a constant is the constant.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»k«/mi»«mo»=«/mo»«mi»k«/mi»«/mrow»«/mstyle»«/math»,
where «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mi»k«/mi»«/mstyle»«/math» is a constant.
Property 6 – The limit of a constant multiplied by a function is the constant multiplied by the limit of the function.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»k«/mi»«mi mathvariant=¨normal¨» «/mi»«mi»f«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mi»k«/mi»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math»
Property 7 – The limit of a power is the power of the limit.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«msup»«mfenced open=¨[¨ close=¨]¨»«mrow»«mi»f«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mfenced»«mi»n«/mi»«/msup»«mo»=«/mo»«msup»«mfenced open=¨[¨ close=¨]¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mfenced»«mi»n«/mi»«/msup»«/mrow»«/mstyle»«/math», where «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»n«/mi»«mo»§#8712;«/mo»«mi»N«/mi»«/mrow»«/mstyle»«/math»
Property 8 – The limit of a root is the root of the limit.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mroot»«mrow»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi
mathvariant=¨normal¨»)«/mi»«/mrow»«mi»n«/mi»«/mroot»«mo»=«/mo»«mroot»«mrow»«munder»«mi»lim«/mi»«mrow»«mi»x«/mi»«mo»§#8594;«/mo»«mi»c«/mi»«/mrow»«/munder»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«mi»n«/mi»«/mroot»«/mrow»«/mstyle»«/math»