Geographically, the southeast and northwest refer to four directions, that is, the direction facing Polaris is north, the back is south, the right hand is east, and the left hand is west; Mathematically, southeast, northwest and northwest refer to four directions, which are expressed by two-dimensional coordinates, that is, the positive direction of abscissa is east, the reverse direction is west, and the positive direction of ordinate is north and the reverse direction is south.

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How to distinguish between southeast and northwest: Compass is a tool to indicate the direction, which is widely used in various directions, such as navigation, field exploration, urban road map reading and so on. It is also an indispensable tool for mountaineering exploration. Its basic function is to use the earth's magnetic field to indicate the north direction. It must find the relative position with the map to know its position.

It has the same function as a compass. The north pole of the magnetic needle points to the geographical north pole, which can be used to identify the indicating direction. But in some parts of the world, compasses are also called compasses.