View Full Version : Differentiate: f(t)= ln(t^2√(2-t))
Dodo333
May 1, 2013, 05:43 AM
Please differentiate: f(t)= ln(t^2√(2-t)) using dt/dx
ebaines
May 1, 2013, 05:57 AM
Please differentiate: f(t)= ln(t^2√(2-t)) using dt/dx
I'm guessing that you are alluding to the chain rule:
\frac {df}{dt} = \frac {df}{dx} \ \frac {dx} {dt}
Here let x = t^2 \sqrt{2-t}, so that f = ln(x). Now apply the chain rule - what do you get?
Dodo333
May 1, 2013, 06:02 AM
I'm guessing that you are alluding to the chain rule:
\frac {df}{dt} = \frac {df}{dx} \ \frac {dx} {dt}
Here let x = t^2 \sqrt{2-t}, so that f = ln(x). Now apply the chain rule - what do you get?
Hello, thanks for your answer, but I really do not know how do this, I just know that the answer must be obtained using dt/dx. Please let me know the solution with the steps, I would really appreciate that.
ebaines
May 1, 2013, 06:32 AM
I won't give you the answer, but I'll show you how to do a similar problem. Let me know if there are any steps here that you don't understand:
Differentiate: f(t) = sin(t^3 \sqrt t )
1. Let x = t^3 \sqrt t.
2. f = \sin (x), hence \frac {df}{dx} = \cos(x) = \cos(t^3 \sqrt t)
3. \frac {dx}{dt} = \frac {d( t^3 \sqrt t )}{dt} = 3t^2 \sqrt t - \frac {t^3} {2\sqrt t}
4. \frac {df}{dt} = \frac {df}{dx} \ \frac {dx}{dt} = \cos(t^3 \sqrt t ) (3t^2 \sqrt t - \frac {t^3} {2\sqrt t} )
You can apply this same technique to your problem. Post back with what you get for an answer.