Derivative of the square root of the function f(x squared)

In summary: You could also have tried ##f(x) = \sin^2 x##, where ##f'(x) = 2 \sin x \cos x##. Then we have: $$k(x) = \sqrt{f(x^2)} = \sin x^2$$ and $$k'(x) = 2x \cos x^2$$ Then, using your formula we have: $$k'(x) = \frac 1 2 \frac 1 {\sin x^2} (2\sin x^2 \cos x^2) (2x) = 2x \cos x^2$$ PS Check the derivative of ##\sin x##.
  • #1
Strand9202
10
2
Homework Statement
I was asked to find the derivative of the sqrt (f(x^2)).
Relevant Equations
Chain Rule
I started out by rewriting the function as (f(x^2))^(1/2). I then did chain rule to get 1/2(f(x^2))^(-1/2) *(f'(x^2).

- I think I need to go further because it is an x^2 in the function, but not sure.
 
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  • #2
Strand9202 said:
- I think I need to go further because it is an x^2 in the function, but not sure.
Yes, you do. Effectively you have ##g(f(h(x)))##, where ##g(x) = x^{1/2}## and ##h(x) = x^2##.
 
  • #3
PeroK said:
Yes, you do. Effectively you have ##g(f(h(x)))##, where ##g(x) = x^{1/2}## and ##h(x) = x^2##.
Would I be wise and just restarting all over again, or should I just pick up from where I left off.
 
  • #4
Strand9202 said:
Would I be wise and just restarting all over again, or should I just pick up from where I left off.
That's up to you.
 
  • #5
Strand9202 said:
Homework Statement:: I was asked to find the derivative of the sqrt (f(x^2)).
Relevant Equations:: Chain Rule

I started out by rewriting the function as (f(x^2))^(1/2). I then did chain rule to get 1/2(f(x^2))^(-1/2) *(f'(x^2).

- I think I need to go further because it is an x^2 in the function, but not sure.

I have tried and gone further. I got to the final answer of
1/2(f(x^2))^(-1/2) *f'(x^2)*2x

Is that my final answer now?
 
  • #6
PeroK said:
That's up to you.
I have tried and gone further. I got to the final answer of
1/2(f(x^2))^(-1/2) *f'(x^2)*2x
 
  • #7
Strand9202 said:
I have tried and gone further. I got to the final answer of
1/2(f(x^2))^(-1/2) *f'(x^2)*2x
Here's an idea. Try with ##f(x) = ## some function and see whether you get the right answer.
 
  • #8
PeroK said:
Here's an idea. Try with ##f(x) = ## some function and see whether you get the right answer.
I did that. I let f(x)=sin. That way my overall function reads square root (sin(x^2)). I got that my final answer was 1/2(sin(x^2))^(-1/2) * -cos(x^2)*2x. Which does fit with my rule. Therefore that shows my answer is correct.
 
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  • #9
Strand9202 said:
I did that. I let f(x)=sin. That way my overall function reads square root (sin(x^2)). I got that my final answer was 1/2(sin(x^2))^(-1/2) * -cos(x^2)*2x. Which does fit with my rule. Therefore that shows my answer is correct.
You could also have tried ##f(x) = \sin^2 x##, where ##f'(x) = 2 \sin x \cos x##. Then we have: $$k(x) = \sqrt{f(x^2)} = \sin x^2$$ and $$k'(x) = 2x \cos x^2$$ Then, using your formula we have: $$k'(x) = \frac 1 2 \frac 1 {\sin x^2} (2\sin x^2 \cos x^2) (2x) = 2x \cos x^2$$ PS Check the derivative of ##\sin x##.
 

1. What is the derivative of the square root of the function f(x squared)?

The derivative of the square root of the function f(x squared) is equal to 1/2 times the reciprocal of the square root of f(x squared) multiplied by the derivative of f(x squared).

2. How do you find the derivative of the square root of a function?

To find the derivative of the square root of a function, you can use the power rule and chain rule. First, rewrite the function as f(x)^(1/2) and then apply the power rule to get 1/2*f(x)^(-1/2). Next, use the chain rule to multiply by the derivative of the function inside the square root.

3. Can the derivative of the square root of a function be negative?

Yes, the derivative of the square root of a function can be negative. This will occur when the function inside the square root is decreasing, causing the derivative to be negative.

4. What is the difference between the derivative of the square root of a function and the square root of the derivative of a function?

The derivative of the square root of a function is the slope of the tangent line at a specific point on the function, while the square root of the derivative of a function is a function itself. The two may have different values at different points on the original function.

5. Can the derivative of the square root of a function be undefined?

Yes, the derivative of the square root of a function can be undefined. This will occur when the function inside the square root is equal to zero, as the reciprocal of zero is undefined.

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