# Homework Help: Trapezoidal Rule

1. May 8, 2012

### iRaid

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

Part b.

2. Relevant equations

3. The attempt at a solution
Well I thought the trapezoidal rule was:
$$\int_a^b f(x)dx = \frac{b-a}{2n}[f(1)+2f(2)+2f(3)+...+f(n)]$$

But when I did that I got the wrong answer and the work shows a completely different formula that I didn't know:

The part I'm confused about is the (2((66+60)/2)+....)

2. May 8, 2012

### Staff: Mentor

(66+60)/2 is the avg height and 2 is thw dith of the segment so then 2*(66+60)/2 = area of that segment. add them up to get the approx area under the curve.

3. May 8, 2012

### iRaid

Why is there an 2, then 3, then 4, then1 infront of each of the areas of the segments :|

4. May 8, 2012

### Staff: Mentor

The first subinterval is of width 2 (sec); the 2nd's width is 3 sec; the 3rd's width is 4 sec; the last subinterval's width is 1.