Numerical Analysis of Engineering Systems - Answers

1. Write the statements required to write VBA function code to compute the integral shown in the equations to the right. Use the following header for your function: Function myInt (a as Double, b as Double, _ n as Double) as Variant Because the type of the function is Variant, it can return either a numerical value or a string message “Undefined” if the integral is undefined. Function myInt(a As Double, b As Double, _ n As Double) As Variant If n <> -1 Then myInt = (b ^ (n + 1) _ - a ^ (n + 1)) / (n + 1) ElseIf a * b > 0 Then myInt = Log(b / a) Else myInt = "Undefined" End If End Function  b n 1  a n 1 n  1  n  1   b  b n a x dx  ln  a  n  1 and ab  0   undefined if   n  1 and ab  0  2. The spreadsheet shown below the equations will be used to call your VBA function. Write the Excel statements necessary to determine the integral, using the function above, in cells B4:E4. Write the formula =myInt(B1, B2, B3) in cell B4 and copy the formulas to cells C4:E4. 3. What values would you get in cells F1:F3 if you entered the formula =myInt(C1, D1, E1) in cell F1 and copied that formula to cells F2 and F3? For cell F1 the formula myInt(C1, D1, E1) gives a = 1, b = 2, and n = 1 so that the integral is [2^(1+1) – 1^(1+1)]/(1+1) = (4 – 1) / 2 = 1.5 For cell F2 the copied formula becomes myInt(C2, D2, E2) which gives a = 2, b = -2, and n = 1 so that the integral is [2^(2+1) – (-2)^(1+1)]/(1+1) = (4 – 4) / 2 = 0 For cell F3 the copied formula becomes myInt(C3, D3, E3) which gives a = -1, b = -1, and n = 4 so that the integral is [(-1)^(2+1) – (-1)^(1+1)]/(4+1) = (1 – 1) / 5 = 0