1 In the triangle \(A B C\), the length \(A B = 6 \mathrm {~cm}\), the length \(A C = 15 \mathrm {~cm}\) and the angle \(B A C = 30 ^ { \circ }\).
- Calculate the length \(B C\).
\(D\) is the point on \(A C\) such that the length \(B D = 4 \mathrm {~cm}\). - Calculate the possible values of the angle \(A D B\).