ข้อสอบคณิต O-NET - 2551

$\mathrm{จากรูป}$

$$\begin{gathered} \mathrm{จะได้} \hat{1} = \hat{5} \\ \hat{3}+\hat{4} = 90° \\ \hat{5}+\hat{4} = 90° \\ \mathrm{จะได้} \hat{3} = \hat{5} \\ \hat{2}+\hat{3} = 90° \\ \hat{4}+\hat{3} = 90° \\ \mathrm{จะได้} \hat{2} = \hat{4} \end{gathered}$$

$$\begin{gathered} \mathrm{จาก} \hat{2}+\hat{3} = 90° \\ A+B = 90° \\ \mathrm{จะได้้} \sin A = \cos B \\ \tan A = cotB \\ secA = \cos ecB \\ \mathrm{ดังนั้น} \mathrm{ข้อ} 3 \sin \left(\hat{2}\right) = \cos \left(\hat{4}\right) \mathrm{ถูก} \end{gathered}$$