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btsjungkookarmy0710
2 năm trước
Cho tam giác ABC vuông tại A có góc B = 60, AB = a Tính tích vô hướng AC.CB Làm ntn có sai ko: Có tan(60) = AC /AB => AC= a√(3) Áp dụng định lí Pi-ta-go trong tam giác ABC ta có: BC^2=AC^2 + AB^2 => BC=2a Lại có: tishc vô hướng AC.CB = AC^2 + BC^2 - AB^2 / 2 = 3a^2
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