# Homework Help: Finding the equation for the tangent line.

1. Jul 17, 2007

### cd246

1. The problem statement, all variables and given/known data
find the equation for the tangent line.
1. (e^x)(cos x) where x=0

2. Relevant equations
plugged 0 into the equation, (e^0)(cos 0) and got 1 for the y-coordinate. so I got the points(0,1). For the slope, I derived the equation into -(e^x)(sin x). then i plugged 0 in and got 0 for the slope.
I used point-slope form, y-1=0(x-0)

3. The attempt at a solution
y-1=0(x-0) or y=1.
I believe the slope was suppose to be 1 and I got 0, what is the right way to get the slope?

Last edited: Jul 17, 2007
2. Jul 17, 2007

I doubt anyone will help you until you post a more complete problem statement.

3. Jul 17, 2007

### Staff: Mentor

Sorry, I'm not tracking what you are trying to do. Are you saying that you have the following equation:

$$y(x) = {e^x} cos(x)$$

and you want to know what the tangent (derivative) is at x=0? Do you know how to take the derivative of that y(x) function? Also, you won't be plugging in x=0 until you have that final derivative function....

4. Jul 17, 2007

### cd246

I saw my mistake, I did the derivative wrong. sorry

5. Jul 17, 2007

### Staff: Mentor

No need to be sorry. So that means you're okay now?

6. Jul 17, 2007

### cd246

For this problem, Yes

7. Jul 17, 2007

### GoldPheonix

Yeah, you forgot the chain rule.