Start with a slightly higher position in the middle of the upper half of the vertical centerline, and the position of the red marker is shown in the following figure:
Second, write to the right of the midpoint of the upper boundary line and look at the position of the red dot.
Third, when writing radian on the left, don't touch the line on the left, there should be a little gap.
Fourth, when writing the lower right corner, the touch point should be written to the midpoint of the lower half of the vertical centerline.
5. When writing the radian below, touch the midpoint of the lower edge.
6. Touch the midpoint of the lower half of the left line when writing back.
Seven, the intersection point should be at the midpoint of the horizontal center line.
Put pen to paper should fall on the point of writing.
Nine, finally write it clearly again.