This is the problem:
Create a class called 'Triangle' with the following member
functions (public) and variables (private).
Variables  3 lengths  all 3 values are floats.
1 bool  tells if current lengths are valid.
Functions 
Constructor with no arguments (default constructor)  asks user for
3 values and verifies they are valid. (all 3 > 0, sum of any 2
greater than the 3rd.) Keeps asking until it gets valid values.
Constructor with 3 lengths  (3 arguments).
These can be used to "set" values from within a function.
It needs to verify the values are legitimate (all 3 > 0, sum
of any 2 greater than the 3rd.) Stores them even if they are
invalid (stores false in bool argument in this case.)
GetTriangle  "returns" the 3 lengths and boolean value.
Perimeter  returns the sum (float) of the 3 sides.
Equilateral  returns if the triangle is/isn't equilateral (bool)
Right  returns if the triangle is/isn't right (bool)
(overloaded) == operator to test if 2 triangles are similar in size.
Write the classes functions/constructors.
Also write a main function to test the above.
Here is my code so far, I don't know how to use constructors. Can someone please help me.
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#include <iostream>
#include <cmath>
using namespace std;
class Triangle
{
public:
void GetTriangle();
void Perimeter();
void TriangleType();
private:
float sa, sb, sc;
void check_data();
};
int main()
{
Triangle triangle;
triangle.GetTriangle();
triangle.Perimeter();
triangle.TriangleType();
return 0;
}
void Triangle::GetTriangle()
{
// stores the values input by the user.
do
{
cout << "Enter sides of a triangle." << endl;
cin >> sa >> sb >> sc;
check_data();
}while(sa <= 0  sb <= 0  sc <= 0  (sa + sb) < sc);
}
void Triangle::Perimeter()
{
// calculates the perimeter of the triangle.
float perimeter = sa + sb + sc;
cout << "The perimeter is " << perimeter << " units." << endl;
}
void Triangle::check_data()
{
// checks if the values are correct.
if(sa <= 0  sb <= 0  sc <= 0  (sa + sb) < sc)
{
cout << "Incorrect values, try again." << endl;
}
}
void Triangle::TriangleType()
{
// check if the triabgle is an equilateral triangle.
if(sa == sb && sb == sc)
{
cout << "The triangle is an equilateral triangle." << endl;
}
else
{
cout << "The triangle is not an equilateral triangle." << endl;
}
// check if the triangle is a right triangle.
if(sqrt((sa * sa) + (sb * sb)) == sc)
{
cout << "The triangle is a right triangle." << endl;
}
else
{
cout << "The triangle is not a right triangle." << endl;
}
}
 