-Tham khảo:
https://olm.vn/hoi-dap/tim-kiem?q=cho+tam+gi%C3%A1c+ABC.+G%C3%B3c+A+=+30+%C4%91%E1%BB%99+.+D%E1%BB%B1ng+%E1%BB%9F+ngo%C3%A0i+tam+gi%C3%A1c+ABC+tam+gi%C3%A1c+%C4%91%E1%BB%81u+BCD.+CMR:+AD%5E2=AB%5E2+AC%5E2&id=818425
-Mai mốt bạn nhớ đăng cho đúng lớp nhé!