Calculating Cone Surface Area | Step-by-Step Guide

[bobsmith76]

Homework Statement

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

 

[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

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

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

 

[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

 

[bobsmith76]

thanks, I got it.