Math Problem Statement

(a) Find the Riemann sum for f(x) = 5 sin x, 0 ≀ x ≀ 3πœ‹/2, with six terms, taking the sample points to be right endpoints. (Round your answers to six decimal places.) R6 =

Solution

To compute the Riemann sum R6R_6 for the function f(x)=5sin⁑(x)f(x) = 5 \sin(x) over the interval [0,3Ο€2][0, \frac{3\pi}{2}] with 6 subintervals, using right endpoints, follow these steps:

Step 1: Determine the width of each subinterval.

The width of each subinterval, denoted by Ξ”x\Delta x, is calculated as:

Ξ”x=bβˆ’an=3Ο€2βˆ’06=3Ο€26=Ο€4\Delta x = \frac{b - a}{n} = \frac{\frac{3\pi}{2} - 0}{6} = \frac{\frac{3\pi}{2}}{6} = \frac{\pi}{4}

Step 2: Identify the sample points (right endpoints).

The right endpoints are given by:

xi=a+iΞ”xx_i = a + i\Delta x

For i=1,2,…,6i = 1, 2, \dots, 6, the right endpoints are:

x1=Ο€4,x2=Ο€2,x3=3Ο€4,x4=Ο€,x5=5Ο€4,x6=3Ο€2x_1 = \frac{\pi}{4}, \quad x_2 = \frac{\pi}{2}, \quad x_3 = \frac{3\pi}{4}, \quad x_4 = \pi, \quad x_5 = \frac{5\pi}{4}, \quad x_6 = \frac{3\pi}{2}

Step 3: Calculate the function values at these points.

We now evaluate f(x)=5sin⁑(x)f(x) = 5 \sin(x) at each of these right endpoints:

f(x1)=5sin⁑(Ο€4),f(x2)=5sin⁑(Ο€2),f(x3)=5sin⁑(3Ο€4)f(x_1) = 5 \sin\left(\frac{\pi}{4}\right), \quad f(x_2) = 5 \sin\left(\frac{\pi}{2}\right), \quad f(x_3) = 5 \sin\left(\frac{3\pi}{4}\right) f(x4)=5sin⁑(Ο€),f(x5)=5sin⁑(5Ο€4),f(x6)=5sin⁑(3Ο€2)f(x_4) = 5 \sin(\pi), \quad f(x_5) = 5 \sin\left(\frac{5\pi}{4}\right), \quad f(x_6) = 5 \sin\left(\frac{3\pi}{2}\right)

Using the values of sin⁑(x)\sin(x):

f(x1)=5Γ—22,f(x2)=5Γ—1,f(x3)=5Γ—22f(x_1) = 5 \times \frac{\sqrt{2}}{2}, \quad f(x_2) = 5 \times 1, \quad f(x_3) = 5 \times \frac{\sqrt{2}}{2} f(x4)=5Γ—0,f(x5)=5Γ—(βˆ’22),f(x6)=5Γ—(βˆ’1)f(x_4) = 5 \times 0, \quad f(x_5) = 5 \times \left(-\frac{\sqrt{2}}{2}\right), \quad f(x_6) = 5 \times (-1)

Simplifying these:

f(x1)=5Γ—0.707106=3.535534,f(x2)=5,f(x3)=3.535534f(x_1) = 5 \times 0.707106 = 3.535534, \quad f(x_2) = 5, \quad f(x_3) = 3.535534 f(x4)=0,f(x5)=βˆ’3.535534,f(x6)=βˆ’5f(x_4) = 0, \quad f(x_5) = -3.535534, \quad f(x_6) = -5

Step 4: Compute the Riemann sum.

The Riemann sum is given by:

R6=Ξ”x[f(x1)+f(x2)+f(x3)+f(x4)+f(x5)+f(x6)]R_6 = \Delta x \left[ f(x_1) + f(x_2) + f(x_3) + f(x_4) + f(x_5) + f(x_6) \right]

Substitute the values of f(xi)f(x_i) and Ξ”x=Ο€4\Delta x = \frac{\pi}{4}:

R6=Ο€4[3.535534+5+3.535534+0βˆ’3.535534βˆ’5]R_6 = \frac{\pi}{4} \left[ 3.535534 + 5 + 3.535534 + 0 - 3.535534 - 5 \right] R6=Ο€4[3.535534+5+3.535534βˆ’3.535534βˆ’5]R_6 = \frac{\pi}{4} \left[ 3.535534 + 5 + 3.535534 - 3.535534 - 5 \right] R6=Ο€4Γ—3.535534=Ο€4Γ—3.535534R_6 = \frac{\pi}{4} \times 3.535534 = \frac{\pi}{4} \times 3.535534 Now, calculate the result:

R6β‰ˆ2.774R_6 \approx 2.774

Thus, the Riemann sum R6R_6 is approximately 2.7742.774.

Would you like more details on any of the steps? Here are some related questions:

  1. What is the general formula for the Riemann sum?
  2. How do you find left and midpoint Riemann sums?
  3. Can the number of subintervals affect the accuracy of Riemann sums?
  4. What happens when using non-uniform subintervals?
  5. How is the Riemann sum related to the definite integral?

Tip: Increasing the number of subintervals generally increases the accuracy of the Riemann sum approximation to the integral.

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Math Problem Analysis

Mathematical Concepts

Calculus
Riemann Sums
Trigonometric Functions

Formulas

Riemann sum formula: R_n = Ξ£ f(x_i) * Ξ”x
Function: f(x) = 5 sin(x)
Subinterval width: Ξ”x = (b - a) / n

Theorems

Riemann sum approximation to the definite integral
Sine function properties

Suitable Grade Level

Grades 11-12 or Early College