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# Geometry using Complex Numbers in C++ | Set 2

• Last Updated : 18 Jan, 2022

After going through previous post, we know what exactly are complex numbers and how we can use them to simulate points in a cartesian plane. Now, we will have an insight as to how to use the complex class from STL in C++.
To use the complex class from STL we use #include <complex>

Defining Point Class
We can define our point class by typedef complex<double> point; at the start of the program. The X and Y coordinates of the point are the real and imaginary part of the complex number respectively. To access our X- and Y-coordinates, we can macro the real() and imag() functions by using #define as follows:

```# include <complex>
typedef complex<double> point;
# define x real()
# define y imag()```

Drawback: Since x and y have been used as macros, these canâ€™t be used as variables. However, this drawback doesnâ€™t stand in front of the many advantages this serves.

## CPP

 `// CPP program to illustrate ` `// the definition of point class` `#include ` `#include `   `using` `namespace` `std;`   `typedef` `complex<``double``> point;`   `// X-coordinate is equivalent to the real part` `// Y-coordinate is equivalent to the imaginary part` `#define x real()` `#define y imag()`   `int` `main()` `{` `    ``point P(2.0, 3.0);` `    ``cout << ``"The X-coordinate of point P is: "` `<< P.x << endl;` `    ``cout << ``"The Y-coordinate of point P is: "` `<< P.y << endl;`   `    ``return` `0;` `}`

Output:

```The X-coordinate of point P is: 2
The Y-coordinate of point P is: 3```

Implementation of attributes with respect to P single point P in plane:

1. The X coordinate of P: P.x
2. The Y coordinate of P: P.y
3. The distance of P from origin (0, 0): abs(P)
4. The angle made by OP from the X-Axis where O is the origin: arg(z)
5. Rotation of P about origin: P * polar(r, Î¸)

## CPP

 `// CPP program to illustrate` `// the implementation of single point attributes` `#include ` `#include `   `using` `namespace` `std;`   `typedef` `complex<``double``> point;` `#define x real()` `#define y imag()`   `// The constant PI for providing angles in radians` `#define PI 3.1415926535897932384626`   `// Function used to display X and Y coordinates of a point` `void` `displayPoint(point P)` `{` `    ``cout << ``"("` `<< P.x << ``", "` `<< P.y << ``")"` `<< endl;` `}`   `int` `main()` `{` `    ``point P(4.0, 3.0);`   `    ``// X-Coordinate and Y-coordinate` `    ``cout << ``"The X-coordinate of point P is: "` `<< P.x << endl;` `    ``cout << ``"The Y-coordinate of point P is: "` `<< P.y << endl;`   `    ``// Distances of P from origin` `    ``cout << ``"The distance of point P from origin is: "` `<< ``abs``(P) <

Output:

```The X-coordinate of point P is: 4
The Y-coordinate of point P is: 3
The distance of point P from origin is: 5
The squared distance of point P from origin is: 25
The angle made by OP with the X-Axis is: 36.8699 degrees
The point P on rotating 90 degrees anti-clockwise becomes: P_rotated(-3, 4)```
1. Vector Addition: P + Q
2. Vector Subtraction: P â€“ Q
3. Euclidean Distance: abs(P â€“ Q)
4. Slope of line PQ: tan(arg(Q â€“ P))

`point A = conj(P) * Q`
1. Dot Product: A.x
2. Magnitude of Cross Product: abs(A.y)

## CPP

 `// CPP program to illustrate ` `// the implementation of two point attributes` `#include ` `#include `   `using` `namespace` `std;`   `typedef` `complex<``double``> point;` `#define x real()` `#define y imag()`   `// Constant PI for providing angles in radians` `#define PI 3.1415926535897932384626`   `// Function used to display X and Y coordinates of a point` `void` `displayPoint(point P)` `{` `    ``cout << ``"("` `<< P.x << ``", "` `<< P.y << ``")"` `<< endl;` `}`   `int` `main()` `{` `    ``point P(2.0, 3.0);` `    ``point Q(3.0, 4.0);`   `    ``// Addition and Subtraction` `    ``cout << ``"Addition of P and Q is: P+Q"``; displayPoint(P+Q);` `    ``cout << ``"Subtraction of P and Q is: P-Q"``; displayPoint(P-Q);`   `    ``// Distances between points P and Q` `    ``cout << ``"The distance between point P ans Q is: "` `<< ``abs``(P-Q) <

Output:

```Addition of P and Q is: P+Q(5, 7)
Subtraction of P and Q is: P-Q(-1, -1)
The distance between point P ans Q is: 1.41421
The squared distance between point P ans Q is: 2
The angle of elevation for line PQ is: 45 degrees
The slope of line PQ is: 1
The dot product P.Q is: 18
The magnitude of cross product PxQ is: 1```

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