第 4 題
四邊形 \(ABCD\), 已知\(\overline{AB}=16\), \(\overline{BC}=25\), \(\overline{CD}=15\), \(\sin\angle B=\frac{16}{25}\), \(\sin \angle C=\frac{4}{5}\), 試求 \(\overline{AD}\).
解答:
\(\displaystyle \cos B=\pm\sqrt{1-\sin^2B}=\pm\frac{3\sqrt{41}}{25}\)
\(\displaystyle \cos C=\pm\sqrt{1-\sin^2 C}=\pm\frac{3}{5}\)
令 \(B(0,0), C(-25,0)\),則
\(A(16\cos B, 16\sin B), D=(-25+15\cos C, 15\sin C)\)
可得 \(\overline{AD}\) 之值.
答案應該有四個.
至於第 3 題,題目的敘述是不是有缺漏呀?題意不太清楚。==