# Surface area of a cone

1. Feb 5, 2012

### bobsmith76

1. The problem statement, all variables and given/known data

I understand everything except for the part where the -1 pops out of nowhere on step 4. why? how?

2. Feb 5, 2012

### Mentallic

Remember that when you solve an integral, you need to take the integral of the highest value minus lowest value. So if you want to solve

$$\int^{b}_{a}f(x)dx$$

Then you'll have

$$=\left[F(x)\right]^b_a$$

$$=F(b)-F(a)$$

3. Feb 5, 2012

### wukunlin

the 1 is the result of substituting the lower limit of the previous step, ie x = 0, which subtracted from the upper limite of the previous step, x = 1/2

edit: oops. too late

4. Feb 5, 2012

### bobsmith76

thanks, I got it.