杨辉三角形中有数,数中有形,看似简单平凡,却内涵十分丰富,是数与形结合的优质产物.走进杨辉三角,对它的内部结构进一步探究,我们就会挖掘出许多更为有价值的智力资源.1.杨辉三角中的“三角形”例1在图1所示的“三角形”中,第9行最中间的数是____.解由C_2~1=2,可知该“三角形”中的第1行对应杨辉三 Yang Hui triangle, the number of tangible, seemingly simple and ordinary, but the connotation is very rich, is the combination of number and shape of quality products. Into Yang Hui Triangle, its internal structure to further explore, we will dig out many more Value of intellectual resources .1 Yang Hui triangle in the “triangle” in Example 1 “triangle” shown in Figure 1, the middle line of the ninth line is ____. Solution by C_2 ~ 1 = 2, We can see that the “triangle” in the first line corresponds to Yang Hui three