Derivative of function h(t) = sin(arccos(t)) - help

In summary: My teacher wants us to find the derivative without using the chain rule.y = xarcsinx + sqrt 1-x^2y = xarcsinx + (1-x^2)^1/2y' = x(1/sqrt1-x^2) + 1/2(1-x^2)^-1/2 * (2x)In summary, y' = x(1/sqrt1-x^2) + 1/2(1-x^2)^-1/2 * (2x) is the derivative of y with respect to x.
  • #1
BuBbLeS01
602
0

Homework Statement


find the derivative of the function:
h(t) = sin (arccos t)


2. The attempt at a solution
derivative of sin = cos
derivative of arccos t:
(-1/sqrt 1-t^2) * 1

my book has a complete different answer so I need some help please.
 
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  • #2
BuBbLeS01 said:

Homework Statement


find the derivative of the function:
h(t) = sin (arccos t)


2. The attempt at a solution
derivative of sin = cos
derivative of arccos t:
(-1/sqrt 1-t^2) * 1

my book has a complete different answer so I need some help please.

did u try chain rule?
 
  • #3
Yes I got...
-1 * (1-t^2)^-1/2 + (2t)
(cos) * 1/2 * (1-t^2)^-3/2 + (2t)
 
  • #4
BuBbLeS01 said:
Yes I got...
-1 * (1-t^2)^-1/2 + (2t)
(cos) * 1/2 * (1-t^2)^-3/2 + (2t)

no that is incorrect... chain rule will be cos u *du where u in this case arcos(t)..
try again...
 
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  • #5
real10 said:
no that is incorrect... chain rule will be sin u *du where u in this case arcos(t)..
try again...

No, it won't. BuBbLeS01's first solution was much closer. Derivative of sin(f(t)) is cos(f(t))*f'(t). Let f be arccos.
 
  • #6
Dick said:
No, it won't. BuBbLeS01's first solution was much closer. Derivative of sin(f(t)) is cos(f(t))*f'(t). Let f be arccos.

hmm I am getting [tex]\frac{-x}{(1-x^2)^(1/2)}[/tex] which I believe is right unless i read the question incorrectly!..
aaah a typo I have corrected the typo should be cos.thanks for pointing that out!
 
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  • #7
I'll let BuBbLeS01 check that.
 
  • #8
real10 said:
hmm I am getting [tex]\frac{-x}{(1-x^2)^(1/2)}[/tex] which I believe is right unless i read the question incorrectly!..
aaah a typo I have corrected the typo should be cos.thanks for pointing that out!
Yes that's right...where did cos go?
 
  • #9
BuBbLeS01 said:
Yes that's right...where did cos go?
Is this right?
cos (arccos t) * cos(-1/sqrt 1-t^2) * (2t)
My teacher does not want our answers simplified at all.
 
  • #10
You are mixing up arccos and it's derivative. cos(arccos(t))=t. cos and arccos are inverse functions, right? The derivative of sin(f(t))=cos(f(t))*f'(t). That's the chain rule. Now carefully put f=arccos.
 
  • #11
Okay, we have:
1. [tex]h(t)=\sin(arccos(t))[/tex]

2. [tex]\frac{d}{dx}\sin(x)=\cos(x)[/tex]

3. [tex]\frac{d}{dt}arccos(t)=\frac{-1}{\sqrt{1-t^{2}}}[/tex]

4. [tex]\cos(arccos(t))=t[/tex]

Agreed?

Thus, by the chainrule, setting [itex]x(t)=arccos(t)[/itex], we have:
[tex]\frac{dh}{dt}=\cos(x(t))\frac{dx}{dt}=-\cos(arccos(t))\frac{1}{\sqrt{1-t^{2}}}=-\frac{t}{\sqrt{1-t^{2}}}[/tex]
 
  • #12
cos (arccos t) * (-1/sqrt 1-t^2)
 
  • #13
BuBbLeS01 said:
cos (arccos t) * (-1/sqrt 1-t^2)

Correct!

Now, what does cos(arcos(t)) simplify to?
 
  • #14
Ok so cos(arccos(t)) simplifies to 1 because they are inverses of each other. I am sorry it has been a while since I have had precalc so I rusty
 
  • #15
BuBbLeS01 said:
Ok so cos(arccos(t)) simplifies to 1 because they are inverses of each other. I am sorry it has been a while since I have had precalc so I rusty
No, it simplifies to..t, not 1!
They are functional inverses, not multiplicative inverses.
 
  • #16
ok so anytime I have like sin(arcsin(t)) it just cancels to t?
 
  • #17
Sure, just like (sqrt(t))^2=t.
 
  • #18
Okay I have another similar problem...
Find the derivative of...
tan(arcsint)
can I use the product rule?
 
  • #19
It's not a product. Use the chain rule.
 
  • #20
sec^2(arcsint) * (1/sqrt1 + t^2)
 
  • #21
That's correct. If your teacher doesn't want you to simplify, I guess you can stop there.
 
  • #22
Dick said:
That's correct. If your teacher doesn't want you to simplify, I guess you can stop there.
Oh yay! thanks...lol
 
  • #23
BuBbLeS01 said:
Oh yay! thanks...lol
Okay I got another one :)...I am getting a different answer then calcchat because I did it differently...
Find the derivative...
y = xarcsinx + sqrt 1-x^2
y = xarcsinx + (1-x^2)^1/2
y' = x(1/sqrt1-x^2) + 1/2(1-x^2)^-1/2 * (2x)
 

FAQ: Derivative of function h(t) = sin(arccos(t)) - help

What is the derivative of the given function?

The derivative of a function is the rate of change of the function with respect to its independent variable. In this case, the derivative of h(t) = sin(arccos(t)) is [-sin(arccos(t))] * [-1/sqrt(1-t^2)] or simply cos(arccos(t)) * 1/sqrt(1-t^2).

How do you find the derivative of a trigonometric function?

To find the derivative of a trigonometric function, you can use the chain rule, product rule, or quotient rule depending on the specific function. In this case, we use the chain rule to find the derivative of h(t) = sin(arccos(t)).

What is the chain rule?

The chain rule is a method used to find the derivative of a composite function. It states that the derivative of a composite function is equal to the derivative of the outer function evaluated at the inner function, multiplied by the derivative of the inner function.

Can you simplify the derivative of the given function?

Yes, the derivative of h(t) = sin(arccos(t)) can be simplified to cos(arccos(t)) * 1/sqrt(1-t^2). Using the identity sin(arccos(t)) = sqrt(1-t^2), we can further simplify the derivative to 1/sqrt(1-t^2).

How can I use the derivative of this function in real-world applications?

The derivative of a function represents the instantaneous rate of change of the function. In real-world applications, this can be used to model and analyze various phenomena, such as the growth or decay of a population or the speed of an object. In this specific case, the derivative of h(t) = sin(arccos(t)) can be used to find the instantaneous velocity of an object moving along a circular path at a given time t.

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