bakit sinabi kong kayo ANG mag isip-why did i say you do the thinking
bakit sinabi kong mag isip kayo-why did i say THINK.
bakit sinabi kong kayo ANG mag isip at hindi ako.-why did i say you do the thinking instead of me doing it.
ANG points the one who is assigned to do the thinking, usually said when the speaker dont want to do the thinking and delegates the task to the listeners.
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in lazy tagalog you can say BAKIT SINABI KONG KAYO MAG ISIP, it means the same: why did i say you do the thinking instead of me doing it.
its opposite to BAKIT SINABI KONG MAG ISIP KAYO because it didnt have a sign that the speaker didnt want to do the task of thinking, he just want to make the listeners think.