Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Choose the letter A, B, C or D to indicate the word that differs from the other three in the position of stress in each of the following questions.

Một người thợ đang cố gắng đặt tấm kính ABCD (mép AB không song song với CD) dựa vào tường sao cho mép kính CD song song với đường chân tường, còn mép kính AB nằm hoàn toàn trên tường. Sau một hồi loay hoay, người thợ vẫn không thể đặt được tấm kính như mong muốn. Hãy giải thích tại sao.

Có cách nào đặt tấm kính để một mép kính song song với đường chân tường, một mép kính khác nằm hoàn toàn trên tường không?

Cho hình hộp ABCD.A'B'C'D'. Gọi M, N, P, Q lần lượt là trung điểm của các cạnh AA', BB', CC', DD'. Chứng minh rằng bốn điểm M, N, P, Q đồng phẳng và MNPQ là hình bình hành.

b) Giả sử MN không song song với BC. Xác định giao tuyến của hai mặt phẳng (MNN'M') và (BCC'B').

Cho hình lăng trụ tứ giác ABCD.A'B'C'D'. Gọi M, N, M', N' lần lượt là trung điểm của các cạnh AB, CD, A'B', C'D'.

a) Chứng minh rằng bốn điểm M, N, M', N' đồng phẳng và tứ giác MNN'M' là hình bình hành.

c) Xác định giao điểm của đường thẳng BO và mặt phẳng (SAC).

b) Xác định giao tuyến của hai mặt phẳng (SBO) và (SAC).

Cho hình chóp S.ABCD có đáy ABCD là hình thang (AB // CD). Gọi O là một điểm nằm trong tam giác SAD.

a) Xác định giao điểm của đường thẳng AO và mặt phẳng (SCD).

d) Chứng minh rằng giao tuyến của hai mặt phẳng (ECD) và (FAB) song song với giao tuyến của hai mặt phẳng (EAB) và (FCD).