Method 1:

The use formula of the number of triangles is: when n is odd, s = (n+1) (2n 2+3n-1)/8; When n is an even number, S=n(n+2)(2n+ 1)/8, and a triangle is a closed figure composed of three line segments in the same plane but not on the same straight line. Ordinary triangles are divided into ordinary triangles (three sides are unequal) and isosceles triangles (isosceles triangles with unequal waist and equal waist and bottom). According to the angle, there are right triangle, acute triangle and obtuse triangle. Among them, acute triangle and obtuse triangle are collectively called oblique triangle, and triangles can often be seen in mathematical problems.

Method 2:

Number each small part first, then count the number of individual triangles, then count the number of triangles consisting of two parts, and finally count the number of triangles consisting of three parts ... and so on, write down which number or numbers each triangle is. Finally, find out how many triangles there are, and add all the numbers together to get the total number of triangles.

Method 3:

First, don't look at the horizontal line in the middle. First, calculate how many small triangles there are in a triangle without a horizontal line. Then, each independent triangle is marked in turn by the cumulative number method, and m triangles are obtained by adding them. Then count the horizontal lines and see how many layers the triangle is divided by the horizontal lines. Let's multiply several layers by m ... If the horizontal lines in the graph are not parallel, we need a number one by one.