Cho tam giác DEF vuông tại D, DE < DF. Lấy điểm M trên cạnh huyền EF sao cho ME > MF. Kẻ MN vuông góc với DE tại N, kẻ MP vuông góc với DF tại P. a. Chứng minh tứ giác DNMP là hình chữ nhật; b. Gọi I là giao điểm của DM và NP, gọi Q và K lần lượt là trung điểm của DE và DF. Chứng minh QI song song với EF và ba điểm Q, I, K thẳng hàng; c. Kẻ đường cao DH của tam giác DEF. Tính tổng góc DNH + góc DPH. Giải giúp mình giải hết 3 câu với ạ!

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