Thread: Help with finding an equation of the tangent of f(x)

1. Help with finding an equation of the tangent of f(x)

Determine the equation of the tangent to y = ln x at x = e

Now I know how to find the equation using a regular function, but where Im confused is how to go about the x = e. Do I read that as e^1 which = 1 and then go from there, or does my final equation have e in it?

Thank You!

2. Originally Posted by Meeklo Braca

Determine the equation of the tangent to y = ln x at x = e

Now I know how to find the equation using a regular function, but where Im confused is how to go about the x = e. Do I read that as e^1 which = 1 and then go from there, or does my final equation have e in it?

Thank You!
dy/dy = 1/x. Therefore m = 1/e. And the point (e, 1) lies on the tangent. Now get the equation of the line in the usual way.

3. Im kind of confused on what to do with this.

I have y - 1 = 1/e(x-e) somehow I get y = x + 1

4. Originally Posted by Meeklo Braca
Im kind of confused on what to do with this.

I have y - 1 = 1/e(x-e) somehow I get y = x + 1
$\displaystyle y - 1 = \frac{1}{e} (x - e) \Rightarrow y - 1 = \frac{x}{e} - 1$. I just don't see how you can get y = x + 1 from this ....

5. Ill try that thank you!