The triangle formed by the lines given by 3x+y=0, 3x−y=0,and  y−2=0

The line y−2=0 is a horizontal line.  The slope of the line 3x+y=0 is m=−3 and the slope of the line 3x−y=0, is m=3 Each acute angle made by these two lines with horizontal line is 60∘It means two angles in a triangle is 60°, therefore, the triangle formed by the given three lines is equilateral triangle.