SEAMO 2020 — Paper E — Lớp 9–10 Câu hỏi 6

Tính $\frac{\cos^4 15^\circ+\sin^4 15^\circ+2\sin^2 15^\circ\cos^2 15^\circ}{\cos^6 15^\circ+\sin^6 15^\circ+3\sin^2 15^\circ\cos^2 15^\circ}$.