A right triangle with coordinates A(−1, 4), B(−1, 8) and C(3, 4) is first rotated 90 degrees counterclockwise and then translated 2 units left and 3 units down to form triangle A'B'C'. What is the measure of angle B'A'C', in degrees, in the resulting figure?

The ∠B prime A prime C prime in the resulting figure = 90°

explanation:
The coordinates of the right triangle = A( -1, 4), B(-1, 8) and C(3, 4)
The rotation 90° counterclockwise of a point on a preimage (x, y) gives the coordinates of the location of the point of the image after rotation as (-y, x)
Therefore we have;
Applying 90° counterclockwise rotation we have;
The point A(-1, 4) is relocated to the point (-4, -1)
The point B(-1, 8) is relocated to the point (-8, -1)
The point C(3, 4) is relocated to the point (-4, 3)

Lie