How do you find the derivative of log_(3)xlog3x?

1 Answer
Mar 15, 2016

frac{"d"}{"d"x}(log_3(x)) = 1/(xln(3))ddx(log3(x))=1xln(3).

Explanation:

There is an identity that states

log_a(b) = frac{ln(a)}{ln(b)}loga(b)=ln(a)ln(b),

for a > 0a>0 and b > 0b>0.

So, we can write

log_3(x) = ln(x)/ln(3)log3(x)=ln(x)ln(3)

for x > 0x>0.

So to find the derivative, it helps if you know that

frac{"d"}{"d"x}(ln(x)) = 1/xddx(ln(x))=1x.

So,

frac{"d"}{"d"x}(log_3(x)) = frac{"d"}{"d"x}(ln(x)/ln(3))ddx(log3(x))=ddx(ln(x)ln(3))

= 1/ln(3) frac{"d"}{"d"x}(ln(x))=1ln(3)ddx(ln(x))

= 1/(xln(3))=1xln(3).