# Find the variable to make the function continuous

1. Sep 4, 2012

### Painguy

1. The problem statement, all variables and given/known data
Find k so that the following function is continuous on any interval.

j(x) = {k cos(x), x ≤ 0
{10ex − k, 0 < x

2. Relevant equations

3. The attempt at a solution
I originally thought i had to check if the limits of both parts of the functions existed, and if so to set them equal to each other, but then I reread the question and realized that it wasn't asking me if its continuous, but to make it continuous by finding the value of k. I figured that i might be able to to set the two functions equal to each other to see if I can get k, but I'm not sure if that's right or not.

2. Sep 4, 2012

### Ray Vickson

For x > 0 do you mean 10*e*x - k, or do you mean 10*ex - k?

RGV

3. Sep 4, 2012

### Bacle2

Maybe to give a 100% answer, just state that right of zero and left of zero there are

no problems of continuity. Then , also, f is continuous if the value at a point coincides

with the right- and left- limits.

4. Sep 4, 2012

### Painguy

I'm sorry i meant 10*ex - k

5. Sep 4, 2012

### SammyS

Staff Emeritus
Chose k to make the following two limits equal to each other.

$\lim_{x\to0^+}\,j(x)\,,$ this is where j(x) = 10ex − k .

$\lim_{x\to0^-}\,j(x)\,,$ this is where j(x) = k cos(x) .

Then make sure that those limits equal j(0) (which of course, they will).

6. Sep 5, 2012

### Painguy

I see. That helps. That's what i intended to to at first, but im not sure how i misinterpreted the question. Anyway thanks for all your help guys