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How would you change both of the codes to cos?
Question

Module Module1
Sub Main()
' declare variables
Dim x, n As Integer
Dim fact, ans, a, b, c As Double
'declare pi
Dim pi As Double = 3.1415926535897931
'ask for and store user input values
Console.WriteLine("Enter 'x' value (degrees): ")
x = Console.ReadLine()
Console.WriteLine("Enter the 'n' degree of the sum: ")
n = Console.ReadLine()
'change x input to radians
c = x * (pi / 180)
'calculation by formula
For a = 0 To n 'establish a value for (2n + 1)!
fact = 1
For b = 1 To ((2 * a) + 1)
fact = fact * b
Next b
'add each term in the series until specified by the user by their n input
ans += ((((1) ^ a) * (c) ^ ((2 * a) + 1)) / fact)
Next a
'output result to user
Console.WriteLine("Sin(" & x & ") = " & ans & " (to " & (n + 1) & " terms). ")
Console.ReadKey()
End Sub
End Module
THE NEXT CODE IS FOR GUI:
Public Class Form1
' This program calculates the value of sin(x) using a truncated series to the nth degree when given x and n
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
End Sub
Private Sub button_calculate(sender As Object, e As EventArgs) Handles Calculate.Click
'declare variables
Dim x, n As Integer
Dim fact, ans, a, b, c As Double
'declare pi
Dim pi As Double = 3.1415926535897931
'ask for and store user input values
x = CInt(Val(Inputbox.Text))
n = CInt(Val(Inputboxn.Text))
'change x input to radians and store as variable c
c = x * (pi / 180)
'calculation by formula
For a = 0 To n 'establish a value for (2n + 1)!
fact = 1
For b = 1 To ((2 * a) + 1)
fact = fact * b
Next b
'add each term in the series until specified by the user by their n input
ans += ((((1) ^ a) * (c) ^ ((2 * a) + 1)) / fact)
Next a
' output calculated sin(x) function to the user
Outputbox.Text = ans.ToString()
End Sub
Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles Inputbox.TextChanged
End Sub
Private Sub button_exit(sender As Object, e As EventArgs) Handles Exit_form.Click
Close() 'allows the user to close the program
End Sub
End Class
Answers

This shows one method in example 1.
http://www.matrixlabexamples.com/sineseries.html
This looks like your equations?
 Proposed as answer by Neda ZhangModerator Wednesday, October 19, 2016 6:10 AM
 Marked as answer by Neda ZhangModerator Wednesday, October 19, 2016 6:10 AM
All replies

As stated in the other post. Also, best to post one question at a time rather than several.
Please remember to mark the replies as answers if they help and unmark them if they provide no help, this will help others who are looking for solutions to the same or similar problem. Contact via my Twitter (Karen Payne) or Facebook (Karen Payne) via my MSDN profile but will not answer coding question on either.
VB Forums  moderator


Hi Improve MSDN,
Thank you for your post.
Firstly, please edit your post and put your code in code block as @Kareninstructor suggested.
Secondly, is it your homework? If yes, please tell us what have you done for this and how do you want us to help you?
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This shows one method in example 1.
http://www.matrixlabexamples.com/sineseries.html
This looks like your equations?
 Proposed as answer by Neda ZhangModerator Wednesday, October 19, 2016 6:10 AM
 Marked as answer by Neda ZhangModerator Wednesday, October 19, 2016 6:10 AM

Hey,
Just posting here as this looks extremely similar to what I am having trouble with.
I am writing a VB program to calculate the cos value of various degree values 'x' using a truncated series. The console application allows the user to enter 'x' and 'n'. The program then calculates cos(theta) by a truncated formula using 'n' first terms of the series.
Using the program I am required to find values for cos(30) and cos(60) for n = 2, 3, 4 and 5. I then need the program to calculate the 'True value' of Cos(theta) using the intrinsic function Math.cos(x). I then need to implement code that uses both the approximated cos value and the true cos value and provide me with a relative percentage error using the formula below.
I am successfully able to calculate the Approximate value of cos(theta) but not too sure how to calculate the true value of cos(theta) using the intrinsic function.
This is what I have so far.
Module Module1 Sub Main() 'Define variables Dim n As Decimal 'n Value Dim i As Decimal 'Counter For Loop Dim theta As Decimal 'Angle / x Value To Be Evaluated Dim Radians As Decimal 'Calculated Radian Value Dim Pi As Double = 3.14159265358979 'Value Of Pi To 14 d.p. Dim k As Single Dim Sum As Single 'Sum Dim Fact As Long 'Factorial Dim f As Long 'Function Dim rel_e As Double 'Relative Error in % Dim v As Double 'True Value Dim v_approx As Double 'Approximated Value 'Input Variables. Console.WriteLine(" Please Enter Value Of 'x' For Cos(x):") 'Asks For input theta = Console.ReadLine() 'Reads input Console.WriteLine("") Console.WriteLine(" Please Enter A Value For n:") 'Asks For Input n = Console.ReadLine() 'Reads Input 'Converts Radians to Degrees Radians = (theta * Pi) / 180 'Relative Error Formula rel_e = (Math.Abs(v)  Math.Abs(v_approx) / Math.Abs(v)) * 100 'VB Intrinsic Function v = Math.Cos(theta) 'Set Sum To 1 And Use A Do Loop To n Sum = 1 For i = 1 To n Fact = 1 f = (2 * i) Do While f > 0 Fact = Fact * f f = f  1 Loop k = ((1) ^ i) * ((Radians ^ (2 * i) / Fact)) 'Truncated Series Sum = Sum + k Next i 'Results Console.WriteLine("") Console.WriteLine("Cos(" & theta & ") = " & Sum) Console.WriteLine("") Console.WriteLine("The Cosine value of 'x' is = " & Math.Cos(theta)) Console.WriteLine("") Console.WriteLine("The Relative Error 'x' is = " & rel_e = (Math.Abs(v)  Math.Abs(v_approx) / Math.Abs(v)) * 100) Console.ReadLine() End Sub End Module
Any help would be greatly appreciated.
Cheers
Mr.Steez

Hey,
Just posting here as this looks extremely similar to what I am having trouble with.
I am writing a VB program to calculate the cos value of various degree values 'x' using a truncated series. The console application allows the user to enter 'x' and 'n'. The program then calculates cos(theta) by a truncated formula using 'n' first terms of the series.
Using the program I am required to find values for cos(30) and cos(60) for n = 2, 3, 4 and 5. I then need the program to calculate the 'True value' of Cos(theta) using the intrinsic function Math.cos(x). I then need to implement code that uses both the approximated cos value and the true cos value and provide me with a relative percentage error using the formula below.
I am successfully able to calculate the Approximate value of cos(theta) but not too sure how to calculate the true value of cos(theta) using the intrinsic function.
This is what I have so far.
Module Module1 Sub Main() 'Define variables Dim n As Decimal 'n Value Dim i As Decimal 'Counter For Loop Dim theta As Decimal 'Angle / x Value To Be Evaluated Dim Radians As Decimal 'Calculated Radian Value Dim Pi As Double = 3.14159265358979 'Value Of Pi To 14 d.p. Dim k As Single Dim Sum As Single 'Sum Dim Fact As Long 'Factorial Dim f As Long 'Function Dim rel_e As Double 'Relative Error in % Dim v As Double 'True Value Dim v_approx As Double 'Approximated Value 'Input Variables. Console.WriteLine(" Please Enter Value Of 'x' For Cos(x):") 'Asks For input theta = Console.ReadLine() 'Reads input Console.WriteLine("") Console.WriteLine(" Please Enter A Value For n:") 'Asks For Input n = Console.ReadLine() 'Reads Input 'Converts Radians to Degrees Radians = (theta * Pi) / 180 'Relative Error Formula rel_e = (Math.Abs(v)  Math.Abs(v_approx) / Math.Abs(v)) * 100 'VB Intrinsic Function v = Math.Cos(theta) 'Set Sum To 1 And Use A Do Loop To n Sum = 1 For i = 1 To n Fact = 1 f = (2 * i) Do While f > 0 Fact = Fact * f f = f  1 Loop k = ((1) ^ i) * ((Radians ^ (2 * i) / Fact)) 'Truncated Series Sum = Sum + k Next i 'Results Console.WriteLine("") Console.WriteLine("Cos(" & theta & ") = " & Sum) Console.WriteLine("") Console.WriteLine("The Cosine value of 'x' is = " & Math.Cos(theta)) Console.WriteLine("") Console.WriteLine("The Relative Error 'x' is = " & rel_e = (Math.Abs(v)  Math.Abs(v_approx) / Math.Abs(v)) * 100) Console.ReadLine() End Sub End Module
Any help would be greatly appreciated.
Cheers
Mr.Steez
This is a double post of the same thing:
Why don't you respond to that thread instead of digging up an unrelated question from a year ago? And address those issues that others brought up?
As noted in the other thread you posted on this you appear to have radians mixed with degrees in some places.
You never assign a value to v_approx, instead you use Sum.