$4.69 \frac{\sin ^{2}(\alpha+\beta)-\sin ^{2} \alpha-\sin ^{2} \beta}{\sin ^{2}(\alpha+\beta)-\cos ^{2} \alpha-\cos ^{2} \beta}$.
4.69 Instruction. Use the formulas for reducing the degree.

Answer: $-\operatorname{tg} \alpha \operatorname{tg} \beta$.