Thread: Inheritance problem

Hello

I am new to the concept of inheritance. So I have a straight forward error I think.
I want to use a protected variable from the base class. But I get an error.
Is there somebody who could tell me how to do it right and wy this doesnt work?
Thank you

Code:

class Vector {
	public:
		Vector(int size);
		void Write(void);
		void Set(int index, double value);
	
	private:
		int length;

	protected:
		double *array;
};

class SpaceVector: public Vector{

	public:
		SpaceVector();
		void Set(double x, double y, double z);
		SpaceVector Cross(SpaceVector &sv2);
};

SpaceVector Cross(SpaceVector &sv2){

	SpaceVector sv3 = SpaceVector();
	double x, y, z;

	x = sv2.array[1];
	return sv3;
}

Vector.h: In function ‘SpaceVector Cross(SpaceVector&)’:
Vector.h:19: error: ‘double* Vector::array’ is protected