In RT △ ABC, if the hypotenuse AB = 5 and the right angle BC = 5, then the area of △ ABC is______ ．

∵ in RT △ ABC, the hypotenuse AB = 5, the right angle BC = 5, the other straight angle AC is AB2 − BC2 = 20, and the area of ∵ ABC is 12 × AC × BC = 5

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