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統計： A(17), B(77), C(21), D(20), E(0) #296495

詳解 (共 1 筆)

#924380
(sin15 + cos15)^2 = (sin15)^2 + (cos15)^2 + 2cos15sin15 = 1 + sin2*15
= 1 + sin30 = 1.5
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