L3 Derivatives of Primary and Reciprocal Trigonometric Functions - Part 3
Completion requirements
Unit 4B
Trigonometry Part 2
Lesson 3: Derivatives of Primary Reciprocal Functions
The derivative of other trigonometric functions can be derived using the derivative rules introduced in Unit 2. Click here for
a summary page of the derivative rules and the primary and reciprocal trigonometric function derivatives.
Find the derivative of «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»h«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mi»sec«/mi»«mi»x«/mi»«/mrow»«/mstyle»«/math».
Rewrite the function as «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»h«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mfrac»«mn»1«/mn»«mrow»«mi»cos«/mi»«mi»x«/mi»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math».
Use the quotient rule to find the derivative.
The function «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»h«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mi»sec«/mi»«mi»x«/mi»«mo»=«/mo»«mfrac»«mn»1«/mn»«mrow»«mi»cos«/mi»«mi»x«/mi»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math» can also be written as «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»h«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»cos«/mi»«mi»x«/mi»«msup»«mi mathvariant=¨normal¨»)«/mi»«mrow»«mo»§#8722;«/mo»«mn»1«/mn»«/mrow»«/msup»«/mrow»«/mstyle»«/math». The chain rule would then be used to find the derivative.
Below is a summary of the derivatives for the six primary and reciprocal trigonometric functions.
Use the quotient rule to find the derivative.
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mtable columnalign=¨right center left¨»«mtr»«mtd»«mi»h«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mfrac»«mn»1«/mn»«mrow»«mi»cos«/mi»«mi»x«/mi»«/mrow»«/mfrac»«/mtd»«/mtr»«mtr»«mtd»«mi»h«/mi»«mo
mathvariant=¨italic¨»`«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mfrac»«mrow»«mi»cos«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»(«/mi»«mn»0«/mn»«mi mathvariant=¨normal¨»)«/mi»«mo»§#8722;«/mo»«mn»1«/mn»«mi
mathvariant=¨normal¨»(«/mi»«mo»§#8722;«/mo»«mi»sin«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«mrow»«msup»«mi»cos«/mi»«mn»2«/mn»«/msup»«mi»x«/mi»«/mrow»«/mfrac»«/mtd»«/mtr»«mtr»«mtd/»«mtd»«mo»=«/mo»«/mtd»«mtd»«mfrac»«mrow»«mi»sin«/mi»«mi»x«/mi»«/mrow»«mrow»«msup»«mi»cos«/mi»«mn»2«/mn»«/msup»«mi»x«/mi»«/mrow»«/mfrac»«/mtd»«/mtr»«mtr»«mtd/»«mtd»«mo»=«/mo»«/mtd»«mtd»«mfrac»«mrow»«mi»sin«/mi»«mi»x«/mi»«/mrow»«mrow»«mi»cos«/mi»«mi»x«/mi»«/mrow»«/mfrac»«mo»§#8729;«/mo»«mfrac»«mn»1«/mn»«mrow»«mi»cos«/mi»«mi»x«/mi»«/mrow»«/mfrac»«/mtd»«/mtr»«mtr»«mtd/»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»tan«/mi»«mi»x«/mi»«mi»sec«/mi»«mi»x«/mi»«/mtd»«/mtr»«/mtable»«/mstyle»«/math»
The function «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»h«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mi»sec«/mi»«mi»x«/mi»«mo»=«/mo»«mfrac»«mn»1«/mn»«mrow»«mi»cos«/mi»«mi»x«/mi»«/mrow»«/mfrac»«/mrow»«/mstyle»«/math» can also be written as «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»h«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»cos«/mi»«mi»x«/mi»«msup»«mi mathvariant=¨normal¨»)«/mi»«mrow»«mo»§#8722;«/mo»«mn»1«/mn»«/mrow»«/msup»«/mrow»«/mstyle»«/math». The chain rule would then be used to find the derivative.
Below is a summary of the derivatives for the six primary and reciprocal trigonometric functions.
| Trigonometric Derivatives
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mtable columnalign=¨right center left center center right center left¨»«mtr»«mtd»«mfrac»«mi»d«/mi»«mrow»«mi»d«/mi»«mi»x«/mi»«/mrow»«/mfrac»«mi»sin«/mi»«mi»x«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»cos«/mi»«mi»x«/mi»«/mtd»«mtd/»«mtd/»«mtd»«mfrac»«mi»d«/mi»«mrow»«mi»d«/mi»«mi»x«/mi»«/mrow»«/mfrac»«mi»csc«/mi»«mi»x«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»-«/mo»«mi»csc«/mi»«mi»x«/mi»«mi»cot«/mi»«mi»x«/mi»«/mtd»«/mtr»«mtr»«mtd»«mfrac»«mi»d«/mi»«mrow»«mi»d«/mi»«mi»x«/mi»«/mrow»«/mfrac»«mi»cos«/mi»«mi»x«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»-«/mo»«mi»sin«/mi»«mi»x«/mi»«/mtd»«mtd/»«mtd/»«mtd»«mfrac»«mi»d«/mi»«mrow»«mi»d«/mi»«mi»x«/mi»«/mrow»«/mfrac»«mi»sec«/mi»«mi»x«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»sec«/mi»«mi»x«/mi»«mi»tan«/mi»«mi»x«/mi»«/mtd»«/mtr»«mtr»«mtd»«mfrac»«mi»d«/mi»«mrow»«mi»d«/mi»«mi»x«/mi»«/mrow»«/mfrac»«mi»tan«/mi»«mi»x«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«msup»«mi»sec«/mi»«mn»2«/mn»«/msup»«mi»x«/mi»«/mtd»«mtd/»«mtd/»«mtd»«mfrac»«mi»d«/mi»«mrow»«mi»d«/mi»«mi»x«/mi»«/mrow»«/mfrac»«mi»cot«/mi»«mi»x«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»-«/mo»«msup»«mi»csc«/mi»«mn»2«/mn»«/msup»«mi»x«/mi»«/mtd»«/mtr»«/mtable»«/mstyle»«/math» |
Find the derivative of «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»«mi»sin«/mi»«mn»2«/mn»«mi»x«/mi»«/mrow»«/mstyle»«/math».
When finding the derivative of a trigonometric function, write the angle in brackets to help distinguish the angle from the function.
To find the derivative, apply the chain rule. Recall the chain rule says to differentiate the outside function, and then multiply the result by the derivative of the inside function.
Consider using the chain rule by identifying an outside function and an inside function. [ Chart Optional ]
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»f«/mi»«mo mathvariant=¨italic¨»`«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«/mrow»«/mstyle»«/math»derivative of the outside function «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mo»§#8729;«/mo»«/mstyle»«/math» derivative of the inside function
The derivative of «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»«mi»sin«/mi»«mfenced»«mrow»«mn»2«/mn»«mi»x«/mi»«/mrow»«/mfenced»«/mrow»«/mstyle»«/math» is «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»f«/mi»«mo mathvariant=¨italic¨»`«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mn»2«/mn»«mi»cos«/mi»«mi mathvariant=¨normal¨»(«/mi»«mn»2«/mn»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math».
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mtable columnalign=¨right center left¨»«mtr»«mtd»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»sin«/mi»«mn»2«/mn»«mi»x«/mi»«/mtd»«/mtr»«mtr»«mtd/»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»sin«/mi»«mi
mathvariant=¨normal¨»(«/mi»«mn»2«/mn»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«/mtr»«/mtable»«/mstyle»«/math»
To find the derivative, apply the chain rule. Recall the chain rule says to differentiate the outside function, and then multiply the result by the derivative of the inside function.
Consider using the chain rule by identifying an outside function and an inside function. [ Chart Optional ]
| Function
|
Derivative
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| Outside 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»«mi»sin«/mi»«mfenced»«mrow»«mo»§#160;«/mo»«mo»§#160;«/mo»«mo»§#160;«/mo»«mo»§#160;«/mo»«mi mathvariant=¨normal¨» «/mi»«/mrow»«/mfenced»«/mrow»«/mstyle»«/math» | «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»f«/mi»«mo mathvariant=¨italic¨»`«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mi»cos«/mi»«mfenced»«mrow»«mo»§#160;«/mo»«mo»§#160;«/mo»«mo»§#160;«/mo»«mo»§#160;«/mo»«mi mathvariant=¨normal¨» «/mi»«/mrow»«/mfenced»«/mrow»«/mstyle»«/math» |
| Inside function
|
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»g«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mn»2«/mn»«mi»x«/mi»«/mrow»«/mstyle»«/math» | «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»g«/mi»«mo mathvariant=¨italic¨»`«/mo»«mfenced»«mi»x«/mi»«/mfenced»«mo»=«/mo»«mn»2«/mn»«/mrow»«/mstyle»«/math» |
«math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»f«/mi»«mo mathvariant=¨italic¨»`«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«/mrow»«/mstyle»«/math»derivative of the outside function «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mo»§#8729;«/mo»«/mstyle»«/math» derivative of the inside function
«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mtable columnalign=¨right center left¨»«mtr»«mtd»«mi»f«/mi»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»sin«/mi»«mi mathvariant=¨normal¨»(«/mi»«mn»2«/mn»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«/mtr»«mtr»«mtd»«mi»f«/mi»«mo mathvariant=¨italic¨»`«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»cos«/mi»«mo»(«/mo»«mo»§#160;«/mo»«mn»2«/mn»«mi»x«/mi»«mo»§#160;«/mo»«mo»)«/mo»«mo»§#8729;«/mo»«mn»2«/mn»«/mtd»«/mtr»«mtr»«mtd/»«mtd»«mo»=«/mo»«/mtd»«mtd»«mi»cos«/mi»«mi mathvariant=¨normal¨»(«/mi»«mn»2«/mn»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»§#8729;«/mo»«mn»2«/mn»«/mtd»«/mtr»«mtr»«mtd/»«mtd»«mo»=«/mo»«/mtd»«mtd»«mn»2«/mn»«mi»cos«/mi»«mi mathvariant=¨normal¨»(«/mi»«mn»2«/mn»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mtd»«/mtr»«/mtable»«/math»
The derivative of «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»«mi»sin«/mi»«mfenced»«mrow»«mn»2«/mn»«mi»x«/mi»«/mrow»«/mfenced»«/mrow»«/mstyle»«/math» is «math style=¨font-family:Verdana¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mstyle mathsize=¨14px¨»«mrow»«mi»f«/mi»«mo mathvariant=¨italic¨»`«/mo»«mi mathvariant=¨normal¨»(«/mi»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«mo»=«/mo»«mn»2«/mn»«mi»cos«/mi»«mi mathvariant=¨normal¨»(«/mi»«mn»2«/mn»«mi»x«/mi»«mi mathvariant=¨normal¨»)«/mi»«/mrow»«/mstyle»«/math».
Watch the video The Chain Rule for additional examples on applying the chain rule to trigonometric functions using both Leibnitz’s notation and Newton’s notation.