Problem

The key is recognizing that the altitude $AD$ creates two right triangles where you can express $AD$ in terms of the sides and angles. Since you're given a specific formula for $AD$ in terms of $a$, $b$, $c$, you need to derive what $AD$ equals using basic trigonometry, then equate it to the given expression to find a relationship between the angles. The constraint $b > c$ and the given angle $\angle C = 23°$ will pin down $\angle B$ uniquely.

The key is recognizing that the altitude $AD$ creates two right triangles where you can express $AD$ in terms of the sides and angles. Since you're given a specific formula for $AD$ in terms of $a$, $b$, $c$, you need to derive what $AD$ equals using basic trigonometry, then equate it to the given expression to find a relationship between the angles. The constraint $b > c$ and the given angle $\angle C = 23°$ will pin down $\angle B$ uniquely.