The appropriate response is equilateral triangle. It is a triangle in which each of the three sides are equivalent. In the natural Euclidean geometry, equilateral triangles are additionally equiangular; that is, every one of the three interior edges are likewise harmonious to each other and are each 60°.
When 2 lines are perpendicular, their slopes are negative reciprocals of one another. Here, if the slope of A is -1/2, the slope of B is +2/1, or just 2.