Cho tam giác \(ABC\) vuông tại \(A\). Biết \(AB{\rm{ }} = {\rm{ 7}}cm,{\rm{ }}AC{\rm{ }} = 21cm.\) Tính các tỉ số lượng giác của góc \(B\) và \(C.\)
A.\(\begin{array}{l}\sin B = \frac{3}{{\sqrt {10} }}\,\,;\,\,\cos B = \frac{1}{{\sqrt {10} }}\,\,;\,\,\tan B = 3\,\,;\,\,\,\cot B = \frac{1}{3}\\\sin C = \frac{1}{{\sqrt {10} }}\,\,;\,\,\cos C = \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan C = \frac{1}{3}\,\,;\,\,\cot C = 3\end{array}\)
B.\(\begin{array}{l}\sin B = \frac{1}{{\sqrt {10} }}\,\,;\,\,\cos B = \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan B = \frac{1}{3}\,\,;\,\,\,\cot B = 3\\\sin C = \frac{3}{{\sqrt {10} }}\,\,;\,\,\cos C = \frac{1}{{\sqrt {10} }}\,\,;\,\,\tan C = 3\,\,;\,\,\cot C = \frac{1}{3}\end{array}\)
C.\(\begin{array}{l}\sin B = \frac{3}{{\sqrt {10} }}\,\,;\,\,\cos B = \frac{7}{{\sqrt {10} }}\,\,;\,\,\tan B = \frac{3}{7}\,\,;\,\,\,\cot B = \frac{7}{3}\\\sin C = \frac{7}{{\sqrt {10} }}\,\,;\,\,\cos C = \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan C = \frac{7}{3}\,\,;\,\,\cot C = \frac{3}{7}\end{array}\)
D.\(\begin{array}{l}\sin B = \frac{7}{{\sqrt {10} }}\,\,;\,\,\cos B = \frac{3}{{\sqrt {10} }}\,\,;\,\,\tan B = \frac{7}{3}\,\,;\,\,\,\cot B = \frac{3}{7}\\\sin C = \frac{3}{{\sqrt {10} }}\,\,;\,\,\cos C = \frac{7}{{\sqrt {10} }}\,\,;\,\,\tan C = \frac{3}{7}\,\,;\,\,\cot C = \frac{7}{3}\end{array}\)
