# How to use trigonometry STL functions in Visual C++

NOTE: Microsoft Visual C++ NET (2002) supported both the managed code model that is provided by the .NET Framework and the unmanaged native Windows code model. The information in this article applies to unmanaged Visual C++ code only.

## Summary

The sample code below illustrates how to use the STL acos, asin, atan, atan2, cos, cosh, sin, sinh, tan, tanh functions in Visual C++.

``   <valarray>   <cmath>``

### Prototype

``// acos     template<class T>     inline valarray<T> acos(const valarray<T>& x);// asin     template<class T>     inline valarray<T> asin(const valarray<T>& x);// atan     template<class T>     inline valarray<T> atan(const valarray<T>& x);// atan2     template<class T>     inline valarray<T> atan2(const valarray<T>& x, const valarray<T>& y);     template<class T>     inline valarray<T> atan2(const valarray<T> x, const T& y);     template<class T>     inline valarray<T> atan2(const T& x, const valarray<T>& y);// cos     template<class T>     inline valarray<T> cos(const valarray<T>& x);// cosh     template<class T>     inline valarray<T> cosh(const valarray<T>& x);// sin     template<class T>     inline valarray<T> sin(const valarray<T>& x);// sinh     template<class T>     inline valarray<T> sinh(const valarray<T>& x);// tan     template<class T>     inline valarray<T> tan(const valarray<T>& x);// tanh     template<class T>     inline valarray<T> tanh(const valarray<T>& x);``
NOTE: The class/parameter names in the prototype may not match the version in the header file. Some have been modified to improve readability.

### Description

This article illustrates the use of STL trigonometry functions through sample code.

### Sample Code

``////////////////////////////////////////////////////////////////////// // // Compile options needed: /GX// // main.cpp : Illustrates the use of STL trigonometry functions.// // Functions:// //  acos, asin, atan, atan2, cos, cosh, sin, sinh, tan, tanh// // Written by Yeong-Kah Tam// of Microsoft Product Support Services,// Copyright (c) 1996 Microsoft Corporation. All rights reserved.////////////////////////////////////////////////////////////////////// #include <iostream>                 // for i/o functions#include <valarray>                 // for valarray#include <cmath>                    // for trigonometry functions#if _MSC_VER > 1020   // if VC++ version is > 4.2   using namespace std;  // std c++ libs implemented in std   #endif #define ARRAY_SIZE  3               // array sizevoid main(){    // Initialize val_array to values -1, 0 and 1.    valarray<double> val_array(ARRAY_SIZE);    for (int i = 0; i < ARRAY_SIZE; i++)        val_array[i] = i - 1;    // Display the size of val_array.    cout << "Size of val_array = " << val_array.size() << endl;    // Display the values of val_array before calling any trigonometry    // functions.    cout << "The values in val_array:" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << val_array[i] << "    ";    cout << endl << endl;    // Initialize rev_valarray that is the reverse of val_array.    valarray<double> rev_valarray(ARRAY_SIZE);    for (i = 0; i < ARRAY_SIZE; i++)        rev_valarray[i] = val_array[ARRAY_SIZE - i - 1];    // Display the size of rev_valarray.    cout << "Size of rev_valarray = " << rev_valarray.size() << endl;    // Display the values of rev_valarray.    cout << "The values in rev_valarray:" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rev_valarray[i] << "    ";    cout << endl << endl;    // rvalue_array to hold the return value from calling the trigonometry    // functions.    valarray<double> rvalue_array;    // ----------------------------------------------------------------    // acos() - display the result of rvalue_array    // ----------------------------------------------------------------    rvalue_array = acos(val_array);    cout << "The result after calling acos():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // asin() - display the result of rvalue_array    // ----------------------------------------------------------------    rvalue_array = asin(val_array);    cout << "The result after calling asin():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // atan() - display the result of rvalue_array    // ----------------------------------------------------------------    rvalue_array = atan(val_array);    cout << "The result after calling atan():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // atan2() - display the result of rvalue_array    // ----------------------------------------------------------------    // This template function returns an object of class valarray<T>,    // each of whose elements at I is the arctangent of x[I] / y[I].    rvalue_array = atan2(val_array, rev_valarray);    cout << "The result after calling atan2(val_array, rev_valarray):"         << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // This template function stores in element I the arctangent of    // x[I] / y.    rvalue_array = atan2(val_array, 3.1416);    cout << "The result after calling atan2(val_array, 3.1416):" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // This template function stores in element I the arctangent of    // x / y[I].    rvalue_array = atan2(3.1416, val_array);    cout << "The result after calling atan2(3.1416, val_array):" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // cos() - display the result of rvalue_array    // ----------------------------------------------------------------    rvalue_array = cos(val_array);    cout << "The result after calling cos():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // cosh() - display the result of rvalue_array    // ----------------------------------------------------------------    rvalue_array = cosh(val_array);    cout << "The result after calling cosh():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // sin() - display the result of val_array    // ----------------------------------------------------------------    rvalue_array = sin(val_array);    cout << "The result after calling sin():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // sinh() - display the result of val_array    // ----------------------------------------------------------------    rvalue_array = sinh(val_array);    cout << "The result after calling sinh():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // tan() - display the result of val_array    // ----------------------------------------------------------------    rvalue_array = tan(val_array);    cout << "The result after calling tan():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;    // ----------------------------------------------------------------    // tanh() - display the result of val_array    // ----------------------------------------------------------------    rvalue_array = tanh(val_array);    cout << "The result after calling tanh():" << endl;    for (i = 0; i < ARRAY_SIZE; i++)        cout << rvalue_array[i] << "     ";    cout << endl << endl;} ``

### Program Output

``Size of val_array = 3The values in val_array:-1    0    1Size of rev_valarray = 3The values in rev_valarray:1    0    -1The result after calling acos():3.14159     1.5708     0The result after calling asin():-1.5708     0     1.5708The result after calling atan():-0.785398     0     0.785398The result after calling atan2(val_array, rev_valarray):-0.785398     0     2.35619The result after calling atan2(val_array, 3.1416):-0.308168     0     0.308168The result after calling atan2(3.1416, val_array):1.87896     1.5708     1.26263The result after calling cos():0.540302     1     0.540302The result after calling cosh():1.54308     1     1.54308The result after calling sin():-0.841471     0     0.841471The result after calling sinh():-1.1752     0     1.1752The result after calling tan():-1.55741     0     1.55741The result after calling tanh():-0.761594     0     0.761594``

## References

For the same information about trigonometry functions, visit the following MSDN Web site:
http://msdn.microsoft.com/en-us/library/a5dh0we3.aspx