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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