(C++) Write a function to compute determinant and check whether a point is contained in a polygon

#include "catch/catch.hpp"
	#include "../polygon.hpp"
	TEST_CASE ("Advanced polygon tests")
	{
	// prepare list of points to create square
	Point points[] = {Point(0,0), Point(0,2), Point(2,2), Point(2,0)};
	Polygon square("Awesome square", points, 4);
	Polygon empty;
	SECTION ("Check for point inside polygon with no vertices")
	{
	CHECK(false == empty.Contains(Point(1,1)));
	}
	SECTION ("Check for point inside polygon")
	{
	CHECK(true == square.Contains(Point(1,1)));
	}
	SECTION ("Check for point outside polygon")
	{
	CHECK(false == square.Contains(Point(-1,-1)));
	}
	SECTION ("Edge cases")
	{
	// at a vertex of the square
	CHECK(true == square.Contains(Point(0,2)));
	// on an edge of the square
	CHECK(true == square.Contains(Point(0,1)));
	}
	}

Help me with Contains function. Thank you.