- #1
moe darklight
- 409
- 0
I thought I should start numbering these... anyway, here's another brain-fart where I miss something obvious:
in the book the dude uses:
[tex]\[
f(x) = \frac{1}{{30}}\sqrt {a^2 + x^2 } + \frac{1}{{60}}(b - x)
\]
[/tex]
later on he continues, using:
[tex]\[
f'(x) = \frac{1}{{30}}\frac{1}{2}(a^2 + x^2 )^{ - 1/2} (2x) - \frac{1}{{60}}
\]
[/tex]
where'd that 2x come from? isn't the derivative of [tex]\[
\sqrt {a^2 + x^2 }
\][/tex] just [tex]\[
\frac{1}{2}(a^2 + x^2 )^{ - 1/2}
\][/tex]?
thanks
in the book the dude uses:
[tex]\[
f(x) = \frac{1}{{30}}\sqrt {a^2 + x^2 } + \frac{1}{{60}}(b - x)
\]
[/tex]
later on he continues, using:
[tex]\[
f'(x) = \frac{1}{{30}}\frac{1}{2}(a^2 + x^2 )^{ - 1/2} (2x) - \frac{1}{{60}}
\]
[/tex]
where'd that 2x come from? isn't the derivative of [tex]\[
\sqrt {a^2 + x^2 }
\][/tex] just [tex]\[
\frac{1}{2}(a^2 + x^2 )^{ - 1/2}
\][/tex]?
thanks
Last edited: