# To estimate: The area of cross section of airplane wing

### Single Variable Calculus: Concepts...

4th Edition
James Stewart
Publisher: Cengage Learning
ISBN: 9781337687805

### Single Variable Calculus: Concepts...

4th Edition
James Stewart
Publisher: Cengage Learning
ISBN: 9781337687805

#### Solutions

Chapter 6.1, Problem 28E
To determine

## To estimate: The area of cross section of airplane wing

Expert Solution

The area of cross section of airplane wing is 4,232cm2_.

### Explanation of Solution

Given information:

The thickness is measured each 20 cm interval.

The general expression for Midpoint Rule is shown below:

abf(x)dxi=1nf(x¯i)Δx=Δx(f(x¯1)+...+f(x¯n))

The interval width is Δx=ban (1)

The midpoint is  x¯i=12(xi1+xi) (2)

Here, width of the subinterval is Δx, the upper limit is b, the lower limit is a, the number of subinterval is n, and the midpoint of (xi1,xi) is x¯i.

Calculation:

Find the width of the subinterval (Δx) using Equation (1) as shown below.

Consider the number of subintervals as 5.

Substitute 5 for n, 200 cm for b, and 0 for a in Equation (1).

Δx=20005=40cm

Let the distance from the left end of the wing be x.

The height of the wing at x is w.

The expression to find the area of the pool for the width x=0 to x=200cm with n=5 using midpoint rule is shown below.

Area=0200wdx=Δx[w(x¯1)+w(x¯2)+w(x¯3)+w(x¯4)+w(x¯5)] (3)

Here, the height of the wing at distance x¯1 is w(x¯1), the height of the wing at distance x¯2 is w(x¯2), the height of the wing at distance x¯3 is w(x¯3), the height of the wing at distance x¯4 is w(x¯4), and the height of the wing at distance x¯5 is w(x¯5).

The end points of the distance intervals are 0, 40 cm, 80 cm, 120 cm, 160 cm, and 200 cm.

The midpoints of the intervals are 20 cm, 60 cm, 100 cm, 140 cm, and 180 cm.

Substitute 40 cm for Δx, 20 cm for x¯1, 60 cm for x¯2, 100 cm for x¯3, 140 cm for x¯4, and 180 cm for x¯5 in Equation (3) as shown below.

Area=40(w(20)+w(60)+w(100)+w(140)+w(180)) (4)

Substitute 20.3 cm for w(20), 29.0 cm for w(60), 27.3 cm for w(100), 20.5 cm for w(140), and 8.7 meter for w(200) in Equation (4) as shown below.

Area=40(20.3+29.0+27.3+20.5+8.7)=40(105.8)=4,232cm2

Therefore, the area of cross section of airplane wing is 4,232cm2_.

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