Question

The direct cosine m is given by formula ____

(a) \(\frac{x_2-x_1}{l_e}\)

(b) \(\frac{y_2-y_1}{l_e}\)

(c) \(\frac{x_1-y_1}{l_e}\)

(d) \(\frac{x_2-y_2}{l_e}\)

The question was asked by my school teacher while I was bunking the class.

This intriguing question comes from Three Dimensional Trusses in section Trusses of Finite Element Method

Answer 1

The correct answer is (b) \(\frac{y_2-y_1}{l_e}\)

The best I can explain: A truss is a two node element which allows arbitrary orientation in XYZ co-ordinate system. The 3D truss element can be treated as straight forward generalization of the 2D truss element.