# Derivatives of Composite Functions: The Chain Rule

TLDRThe chain rule is used to find the derivative of composite functions, those with multiple operations happening at once. To apply it, differentiate the outer function first, treating the inner function as a constant. Then multiply by the derivative of the inner function. Work through composite functions step-by-step, applying the chain rule repeatedly from the outside in. With practice, the chain rule can be combined with other differentiation techniques like the power, product and quotient rules to find derivatives of very complex composite functions.

###### Takeaways

- ๐ The chain rule is used when taking the derivative of a composite function, with an outer and inner function.
- ๐ Apply the chain rule by taking the derivative of the outer function, leaving the inner function alone, then multiply by the derivative of the inner function.
- ๐ The order of operations matters - differentiate the outer function first while leaving the inner function alone.
- ๐งฎ Use the chain rule along with the power rule, product rule or quotient rule when differentiating functions with multiple operations.
- ๐ The chain rule can be applied repeatedly when differentiating functions with many nested operations.
- ๐ Use the chain rule to differentiate complex combinations of polynomial, trigonometric, exponential and other types of functions.
- โ๏ธ Examples show how to apply the chain rule to functions like (x^2 + 1)^(1/2), sin(x^2), (x+3)^2(x^2 - 4)^3
- ๐ค The chain rule works the same with fractional, negative or large exponents.
- ๐ง Understanding and applying the chain rule correctly is crucial for differentiating complicated composite functions.
- ๐ Stay organized, use proper notation, and methodically apply the chain rule to differentiate functions with any number of operations.

###### Q & A

### What is the chain rule and when do we need to use it?

-The chain rule is used when we have to take the derivative of a composite function, meaning there are multiple operations happening within the function. The chain rule allows us to take the derivative by differentiating the outer function first while keeping the inner function the same, then multiplying by the derivative of the inner function.

### What is an example of a composite function that requires the chain rule?

-An example is the function f(x) = โ(x2 + 1). Here there are two functions - the outer function of taking the square root, and the inner function of squaring x and adding 1. To take the derivative using the chain rule, we first differentiate the outer square root function, then multiply by the derivative of the inner (x2 + 1) function.

### How do you apply the chain rule to a function like sin(x2)?

-For sin(x2), the outer function is sine and the inner function is x2. Using the chain rule, we take the derivative of the outer function sin(x) which is cos(x). Then we multiply by the derivative of the inner function x2, which is 2x. Therefore, the final derivative is 2x*cos(x2).

### Does the order of operations matter when applying the chain rule?

-Yes, the order does matter. We must always differentiate the outer function first while treating the inner function as a constant, then multiply by the derivative of the inner function. Doing it in reverse will lead to an incorrect derivative.

### How do you deal with fractional or negative exponents when using the chain rule?

-The rules for fractional and negative exponents still apply. For fractional exponents, bring the exponent down in front and subtract 1 from it. For negative exponents, rewrite as 1 over the positive version. After this, continue applying the chain rule as normal.

### When using the chain rule on a complicated function, how do you stay organized?

-Write out each step carefully, applying the chain rule one operation at a time from the outside in. Use notation properly to distinguish the outer and inner functions. Also, don't manipulate terms until you have found the complete derivative to avoid confusion.

### Can the chain rule be combined with other differentiation rules like the product rule?

-Yes, the chain rule can be combined with other rules when differentiating complicated functions. For example, you may need to use the product rule when differentiating, then use the chain rule to find the derivative of one of the terms from the product rule.

### What happens when you have a function with multiple nested operations like sin(cos(tan(x)))?

-Apply the chain rule repeatedly, working from the outermost function inward. Differentiate the outer function, substitute back in, then differentiate the next inner function using the chain rule again. Continue until you reach the innermost function.

### Can the chain rule work with any type of function?

-Yes, the chain rule can be applied to any composite function regardless of the number or type of operations involved. As long as you methodically apply it from the outside in, the chain rule will give you the correct derivative.

### Why is properly applying the chain rule so important in calculus?

-Most functions we encounter in calculus are composite functions with multiple operations. Without using the chain rule correctly, it would be impossible to differentiate these complex functions that are essential to calculus and its applications.

###### Outlines

##### ๐ Introducing the Chain Rule

This paragraph introduces the chain rule, which is used to find the derivative of composite functions. It explains that when there are multiple operations happening within a function, the chain rule allows you to differentiate the outer function first while treating the inner function as a constant, and then multiply by the derivative of the inner function.

##### ๐งฎ Applying the Chain Rule

This paragraph provides examples of applying the chain rule to find the derivatives of functions involving squared trigonometric functions like sine and cosine. It emphasizes the importance of order when applying the chain rule and shows how to combine it with the power rule and quotient rule.

##### โ๏ธ Using the Chain Rule Repeatedly

This paragraph demonstrates applying the chain rule repeatedly when there are multiple nested functions, using the example of sine of cosine of tangent. It explains working from the outside in, differentiating the outermost function first while treating the inner functions as constants, then multiplying by their derivatives.

###### Mindmap

###### Keywords

##### ๐กChain rule

##### ๐กComposite function

##### ๐กPower rule

##### ๐กProduct rule

##### ๐กQuotient rule

##### ๐กTrigonometric functions

##### ๐กFunction

##### ๐กDerivative

##### ๐กDifferential calculus

##### ๐กNested function

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###### Transcripts

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