The coordinates are given: A (-1; 5) B (-1; -1) C (5; -1). On them you need to build a triangle. What will it look like?

The x-coordinates of points A and B are -1. This means that these points will be located one above the other – point A at height 5, point B – at height – (-1). If you connect them, you get a vertical segment of length YA – YB = 5 – (-1) = 6.

Points B and C have the same coordinate y = -1. If you connect them, you get a horizontal segment, length XC – XB = 5 – (-1) = 6. Since segment AB is perpendicular to segment BC, we have two legs of the same length, which belong to an isosceles right-angled triangle ABC. The tops of sharp corners are directed upward and to the right.