△ABC is reflected across the y-axis on a coordinate plane, resulting in △A′B′C′. If the measure of ∠A is 50 degrees, what is the measure of ∠A′?

Reflections across the line y = x

A reflection across the line y = x switches the x and y-coordinates of all the points in a figure such that (x, y) becomes (y, x). Triangle ABC is reflected across the line y = x to form triangle DEF. Triangle ABC has vertices A (-2, 2), B (-6, 5) and C (-3, 6).