Derivation by first principles: cos(x^0.5)

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Then use the limit definition of the derivative, simplify, and take the limit as h approaches 0 to find the derivative, which is -\frac{1}{2} \sin(\sqrt{x})/x^{1/2}. In summary, to find the derivative of f(x)=cos(√x) by first principles, use the limit definition of the derivative and the binomial expansion of cos(\sqrt{x + h}) to find the derivative to be -\frac{1}{2} \sin(\sqrt{x})/x^{1/2}.
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Homework Statement



Find the derivative of the function f(x)=cos(√x) by first principles

Homework Equations



f'(x)= lim as h tends to zero of [f(x+h)-f(x)]/h

The Attempt at a Solution



Problems arise immediately, since I have no idea what to do with the expression cos(√(x+h)), I've tried binomial expansion, but to no avail. Any help would be greatly appreciated
 
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PedroB said:

Homework Statement



Find the derivative of the function f(x)=cos(√x) by first principles

Homework Equations



f'(x)= lim as h tends to zero of [f(x+h)-f(x)]/h

The Attempt at a Solution



Problems arise immediately, since I have no idea what to do with the expression cos(√(x+h)), I've tried binomial expansion, but to no avail. Any help would be greatly appreciated

[tex]
\cos(\sqrt{x + h}) = \cos(\sqrt{x}(1 + h/x)^{1/2})
[/tex]
and keep the first two terms of the binomial expansion of [itex](1 + h/x)^{1/2}[/itex].
 
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FAQ: Derivation by first principles: cos(x^0.5)

What is derivation by first principles?

Derivation by first principles is a mathematical method used to find the derivative of a function by using the definition of a derivative. It involves taking the limit of the difference quotient as the change in the input variable approaches zero.

Why is derivation by first principles important?

Derivation by first principles allows us to find the exact rate of change of a function at a specific point, without relying on pre-existing knowledge or formulas. It is the most fundamental method for finding derivatives and forms the basis for more advanced techniques.

How do you use derivation by first principles to find the derivative of cos(x^0.5)?

To find the derivative of cos(x^0.5) using first principles, we first write out the definition of a derivative and substitute our function in for f(x). Then, we simplify the difference quotient as much as possible and take the limit as the change in x approaches zero. This will give us the derivative of cos(x^0.5) in terms of x.

What are the advantages of using derivation by first principles?

Derivation by first principles allows for a more precise and accurate calculation of derivatives, as it does not rely on pre-determined formulas that may have limitations. It also helps to deepen our understanding of the concept of derivatives and their applications in mathematics and science.

Are there any limitations to using derivation by first principles?

While derivation by first principles is a powerful and fundamental method for finding derivatives, it can be time-consuming and tedious for more complex functions. In these cases, it may be more efficient to use other methods or pre-existing formulas to find the derivative.

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