# Chain Rule

#### oswald

1. Homework Statement
Finda dw/dt
w=3xy/x²-y²
x=t3
y=e2t

2. Homework Equations
w=(3t3e2t)/(t6-e4t)

3. The Attempt at a Solution
Well,is there anothe way to solve this, instead of dw/dt; like dw/dx * dw/dt + dw/dy * dy/dt ?
1. Homework Statement

2. Homework Equations

3. The Attempt at a Solution

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#### Dick

Science Advisor
Homework Helper
Sure. You could just the chain rule as well. You should get the same answer both ways. Just substituting like you did looks to be a little easier.

#### oswald

Chain Rule Exponential and logarithmic

f(x) = ln [ e^ln(x+1) ]
f' = ?

#### Mark44

Mentor
Simplify it a bit first to make your differentiation easier. What is ln(e^whatever)?

#### oswald

f(x) = ln { e^[ln(x+1)] }

well, i have this answer, but i dont understand
ln [ e^ln(x+1) ] = ln(x+1)

f'(x) = 1/(e^ln(x+1)) * e^ln(x+1) * 1/(x+1) = 1/(x+1)

#### Mark44

Mentor
The ln and exp functions are inverses of one another, so for any real number u, ln(eu) = u. This means that you can simplify your function before taking its derivative. Then, what you end up differentiating is much simpler.

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