Math  /  Calculus

Question田 000162 0003 愺
Question (2) [2 points] a) [0.8[0.8 points ]] Approximate the area under the curve for h(t)h(t) between [1,9][1,9] using a Riemann sum with n=4n=4 sub-intervals. Build your approximation so that each rectangle's height is set from the midpoint of its sub-interval. h(t)=24t+4t12h(t)=\frac{24}{t}+4 t-12

Studdy Solution

STEP 1

What is this asking? We need to estimate the area under a curve using rectangles, specifically the midpoint Riemann sum with four rectangles. Watch out! Don't forget to use the *midpoint* of each sub-interval to determine the rectangle heights, and make sure your calculations are accurate!

STEP 2

1. Find width of each rectangle
2. Find midpoints of each sub-interval
3. Calculate the height of each rectangle
4. Calculate the area of each rectangle
5. Sum the areas

STEP 3

We're given the interval [1,9][1, 9] and n=4n = 4 rectangles.
To find the width of each rectangle, we subtract the starting point from the endpoint and divide by the number of rectangles.
This gives us Δt=914=84=2\Delta t = \frac{9 - 1}{4} = \frac{8}{4} = 2.
So, each rectangle has a width of **2**.

STEP 4

Our sub-intervals are [1,3][1, 3], [3,5][3, 5], [5,7][5, 7], and [7,9][7, 9].
The midpoints are easy to find!
They are **2**, **4**, **6**, and **8**, respectively.

STEP 5

We plug each midpoint into our function h(t)=24t+4t12h(t) = \frac{24}{t} + 4t - 12 to get the height of each rectangle.

STEP 6

For t=2t = 2, h(2)=242+4212=12+812=8h(2) = \frac{24}{2} + 4 \cdot 2 - 12 = 12 + 8 - 12 = 8.

STEP 7

For t=4t = 4, h(4)=244+4412=6+1612=10h(4) = \frac{24}{4} + 4 \cdot 4 - 12 = 6 + 16 - 12 = 10.

STEP 8

For t=6t = 6, h(6)=246+4612=4+2412=16h(6) = \frac{24}{6} + 4 \cdot 6 - 12 = 4 + 24 - 12 = 16.

STEP 9

For t=8t = 8, h(8)=248+4812=3+3212=23h(8) = \frac{24}{8} + 4 \cdot 8 - 12 = 3 + 32 - 12 = 23.

STEP 10

Remember, the area of a rectangle is width times height!
Since our width is consistently **2**, we multiply each height we just calculated by **2**.

STEP 11

Rectangle 1: 28=162 \cdot 8 = 16

STEP 12

Rectangle 2: 210=202 \cdot 10 = 20

STEP 13

Rectangle 3: 216=322 \cdot 16 = 32

STEP 14

Rectangle 4: 223=462 \cdot 23 = 46

STEP 15

Finally, we add up the areas of all the rectangles: 16+20+32+46=11416 + 20 + 32 + 46 = 114.

STEP 16

The approximate area under the curve h(t)h(t) between [1,9][1, 9] using the midpoint Riemann sum with four sub-intervals is **114**.

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