It is isometric because all side lengths and angle measures remained the same.
A transformation is isometric if the transformed image has the same shape has the original image
By careful observation of ΔABC and ΔA'B'C':
AC is symmetrical with A'C'
AB is symmetrical with A'B'
BC is symmetrical with B'C'
<A is symmetrical with <A'
<B is symmetrical with <B'
<C is symmetrical with <C'
Since all the sides and angles are symmetrical after transformation, the transformation is isometric
Learn more here: https://brainly.com/question/7646735