Q. Approximate the definite integral by right Riemann sum with the indicated partitions.y=cosx[0,6π,4π,2π,43π,π]
Problem and Riemann sum setup: Understand the problem and set up the Riemann sum. We are asked to approximate the definite integral of the function y=cos(x) over the interval [0,π] using a right Riemann sum. This means we will use the value of the function at the right endpoint of each subinterval to calculate the sum. The partitions given are [0,π/6,π/4,π/2,3π/4,π], which divide the interval [0,π] into 5 subintervals. We will calculate the width of each subinterval and the value of the function at the right endpoint of each subinterval.
Calculate subinterval widths: Calculate the width of each subinterval.The widths of the subintervals are as follows:- From π/6 to π/4: π/4−π/6=π/12- From π/4 to π/2: π/2−π/4=π/4- From π/2 to 3π/4: 3π/4−π/2=π/4- From 3π/4 to π/40: π/41Note that the first subinterval (from π/42 to π/6) is not used in the right Riemann sum because we are using the right endpoints, and π/42 is the left endpoint of the first subinterval.
Evaluate function at right endpoints: Evaluate the function at the right endpoints of each subinterval.We will evaluate cos(x) at the right endpoints of each subinterval:- cos(4π)=22- cos(2π)=0- cos(43π)=−22- cos(π)=−1
Multiply function values by subinterval widths: Multiply each function value by the width of its subinterval.Now we multiply the value of the function at each right endpoint by the width of the corresponding subinterval:- cos(4π)×(4π−6π)=(22)×(12π)- cos(2π)×(2π−4π)=0×(4π)- cos(43π)×(43π−2π)=(−22)×(4π)- cos(π)×(π−43π)=−1×(4π)
Calculate right Riemann sum: Add up the products to get the right Riemann sum. The right Riemann sum is the sum of all the products calculated in the previous step: R=(2/2)⋅(π/12)+0⋅(π/4)+(−2/2)⋅(π/4)+(−1)⋅(π/4)R=(2/2)⋅(π/12)−(2/2)⋅(π/4)−(π/4)
Simplify Riemann sum: Simplify the Riemann sum.To simplify the Riemann sum, we combine like terms and perform the arithmetic:R=(2/2)×(π/12)−(2/2)×(3π/12)−(π/4)R=(2/2)×(π/12−3π/12)−(π/4)R=(2/2)×(−2π/12)−(π/4)R=(−2/6)×(π)−(π/4)R=−2π/6−π/4
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