# Thread: tangent lines and derivatives...

1. ## tangent lines and derivatives...

find the equation of the tangent line to y=ln(x), x=7

need some help...dont know how to do

thanks

mathaction

2. Originally Posted by mathaction
find the equation of the tangent line to y=ln(x), x=7mathaction
This is the most basic application of the derivative. You simply must get this or you REALLY must reconsider your career goals. If you've been skipping class, I recommend you change that behavior. If you're just not getting it, despite your best efforts, you may wish to have a very serious chat with your academic advisor.

Find the point: (7,ln(7))

Find the first derivative: y' = 1/x

Evaluate the derivative at the given point. m = 1/7

Use the Point-Slope form of a line to write the equation. I'll leave the exercise for you.

Hint: There is a reason why I called the specific value of the derivative "m".

3. Originally Posted by mathaction
find the equation of the tangent line to y=ln(x), x=7
need some help...dont know how to do
Why is that?
Do you know what slope is?
Do you know how derivative relates to slope?
What is y'(7)?