Here is my answer:
(1) points a and d, b and e, c and f.
(2) Because point C and point F are symmetrical points,
∠c = 90 °,
So ∠ f = 90.
(3)∵A and D, B and E, C and F are symmetrical points,
∴AC=DF= 12cm,BC=EF=5cm
∴C△DEF=DE+EF+DF
= 13+5+ 12
=30 cm
∫∠F = 90,
∴DF is the height of ef,
∴S△DEF= 1/2*EF*DF
= 1/2*5* 12
=30(cm^2)
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