Ta có: \(\left\{\begin{array}{l}S A \perp B C \quad(d o S A \perp(A B C)) \\ A B \perp B C(g t)\end{array} \Rightarrow B C \perp(S A B) \Rightarrow B C \perp S B\right.\)

Xét 2 mặt phẳng \((S B C)\) và \((A B C)\) ta có: \(\left\{\begin{array}{l}(S B C) \cap(A B C)=B C \\ S B \perp B C, S B \subset(S B C) \\ A B \perp B C, A B \subset(A B C) \\ S B \cap A B=\{B\}\end{array}\right.\).\(\Rightarrow((S B A) ;(A B C))=(S B, A B)=S B A\)

Xét \(S A B\) tam giác vuông tại \(A\), có \(\tan S B A=\frac{S A}{A B}=\sqrt{3} \Rightarrow S B A=60^{\circ}\).