under construction

= normal (main) tension , = tangential tension , Max [traction(positive)] and minimum [compression(negative)] of normal (main) Tensions and tangent tensions who wheels to right(positive, coming from up the axis) and tangent tensions who wheels to left(negative, coming from down the axis)

,

see the double angle , then

,

verified by and only

then we apply the value of the angle to this equation

working as

and the equation becomes

,

then also

the abscissas (x) and ordinates (y) of the plan chosen in one point of the element (to calculate the stress state in that point), lie grouped together on the abscissa of the circle of Mohr