ข้อสอบคณิต O-NET - 2553

$\mathrm{จากโจทย์} \mathrm{นำมาวาดรูป}$

$$\begin{gathered} \mathrm{จะได้} \tan 45° = \frac{2}{AB} \tan 30° = \frac{2}{AC} \\ 1 = \frac{2}{AB} \frac{1}{\sqrt{3}} = \frac{2}{AC} \\ AB = 2 AC = 2\sqrt{3} \end{gathered}$$

$$\begin{gathered} \mathrm{จะได้} BC = AC-AB \\ = 2\sqrt{3}-2 \\ = 3.46-2 \\ = 1.46 \\ \mathrm{ดังนั้น} \mathrm{ตอบ} 2 \end{gathered}$$