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Rina Pet
ЛА
Людмила Андрианова
D(y) = R \ {cos(x/3) = 0} = R \ {x/3 = +-pi/2 + pik, k E Z} = R \ {x = +-3pi/2 + 3pik, k E Z}
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D(y) = R \ {cos(x/3) = 0} = R \ {x/3 = +-pi/2 + pik, k E Z} = R \ {x = +-3pi/2 + 3pik, k E Z}