![](data:image/png;base64,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)
Một đoạn thẳng AB có độ dài cố định a trượt trên 2 tia Ox và Oy của góc $\widehat{xOy}$ như hình vẽ.
Biết độ dài đoạn thẳng AB là cố định và bằng a. Góc $\widehat{xOy}$ cố định và bằng $\pi/6$.
Xác định độ dài OA để độ dài của OB đạt cực đại. Tính OA, OB khi đó.