Question

Why is it that structures like electric towers make use of triangular shape and not quadrilateral?

Answer 1

It is a property of the triangle that it is not possible to change the length of any side without changing any of the angles of the vertices, and it is not possible to change any of the angles of the vertices without changing the length of a side. 

This is not true of any four-sided figure.

The main reasons are:-
1 ) we know in triangle we have one side less than any quadrilateral  , So cost of tower is less , if we make triangle shape tower .

2 ) If we make quadrilateral shape tower , it will more area and by making triangle shape tower , we can solve this problem  .

3 ) Structures like electric towers make use of triangular shapes and not quadrilaterals as the triangle is very rigid and hence a strong shape. When we push inward at any one vertex of the triangle the triangle does not get distorted.
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overall,we can say:
Triangular shapes are more rigid than quadrilaterals. 
You can try it with straw and see for yourself

Hope this will help you.. :-)

Answer 2

Answer: As the triangle shape is very rigid and hence a strong shape. When we push inward at any one vertex of the triangle the triangle doesn't get distorted

Explanation: