# Differentiation

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• Feb 16th 2009, 03:44 PM
jkami
Differentiation
Check my answers please

1. $f(x)=sin\frac 1{x}$
MY answer: $-\frac 1{x^2}cos\frac 1{x}$

2. $m(x)=e^xsinx$
My answer: $e^xcosx+e^xsinx$

3. $f(x)=ln(x^3-x+9)$
My answer: $\frac {3x^2+1}{x^3-x+9}$

4. $f(x)=ln(e^x+1)$
My answer: $\frac {e^x}{e^x+1}$

5. $u(x)=x arctan x$
My answer: $arctanx+\frac x{x^2+1}$

6. $v(x)=artan(x+1)$
My answer: $\frac 1{(x+1)^2+1}$
• Feb 16th 2009, 03:50 PM
Mush
Quote:

Originally Posted by jkami
Check my answers please

1. $f(x)=sin\frac 1{x}$
MY answer: $-\frac 1{x^2}cos\frac 1{x}$

2. $m(x)=e^xsinx$
My answer: $e^xcosx+e^xsinx$

3. $f(x)=ln(x^3-x+9)$
My answer: $\frac {3x^2+1}{x^3-x+9}$

4. $f(x)=ln(e^x+1)$
My answer: $\frac {e^x}{e^x+1}$

5. $u(x)=x arctan x$
My answer: $arctanx+\frac x{x^2+1}$

6. $v(x)=artan(x+1)$
My answer: $\frac 1{(x+1)^2+1}$

Number 3) should be $\frac {3x^2-1}{x^3-x+9}$, everything else is correct.