Reflect triangle \(A(1,2)\), \(B(4,2)\), \(C(2,5)\) across the \(y\text{-}\text{axis}\). Give the reflection rule, \(\text{all}~\text{three}~\text{image}~\text{vertices}\), congruence result, and orientation change.

Organize a reflection around three checks: the mirror line determines the coordinate rule, every vertex must obey that same rule, and corresponding points must land the same perpendicular distance from the line. Then separate the two geometric conclusions—whether size and shape are preserved, and what happens to the triangle’s cyclic vertex order.