I need my $\sqrt5$ index 2

Let R= Circumradius=85. S= a side. 2 p=vertex angle of an isosceles triangle.
The pentagon is divided into FIVE isosceles triangles with common vertex and R as equal sides and S as base.
Each pair of the above two adjoining triangles, form a quadrilateral with diagonal joining the start of one base and the end of other.
D = Diagonal is the base of an isosceles triangle with R as equal sides and, sum of adjoining pair of vertex angles, as its vertex angle.
For the five triangles, $p=\dfrac S {2*R}$ .
For the quadrilateral the said diagonal also becomes the diagonal of the pentagon, and $\ D=2*R*Sin\{p_n +p_{n+1}\}$ .
In terms of +tive integers, Sum of five D=2R


{Sin(sum of pairs of adjoining verices)}= $\dfrac{2*85*(121992)}{170^2}=\dfrac{3588} 5.$
So a+b=3588 + 5 = 3593.
The sketches explain every thing.