A triangle has vertices P(a,b), Q(c,d), and R(e,f). You are asked to prove that the image triangle angle P'Q'R' of triangle angle PQR after reflection across the y-axis is congruent to the preimage. What coordinates should you use for the vertices of triangle measurements P'Q'R?

Question

A triangle has vertices P(a,b), Q(c,d), and R(e,f).  You are asked to prove that the image triangle angle P'Q'R' of triangle angle PQR after reflection across the y-axis is congruent to the preimage.  What coordinates should you use for the vertices of triangle measurements P'Q'R?

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Anonymous · Answer

The vertices of triangle DEF are D (-5,3), E (4,3), and F (4,-8). What is the area, in square units, of triangle DEF?