Insert a triangle

Wizard for inserting a triangle into the tactile graph. You must enter the coordinates of the three vertices of the triangle: - Coordinates of the first vertex X1 and Y1: pair of values indicating the position of the first vertex of the triangle. - Coordinates of the second vertex X2 and Y2: pair of values indicating the position of the second vertex of the triangle. - Coordinates of the third vertex X3 and Y3: pair of values indicating the position of the third vertex of the triangle. A vertex is defined as the meeting point of two sides of a polygon. The triangle is a three-sided polygon.