Question 1062744
The one decagon is composed of 10 isosceles triangles.


Each base side of one isosceles triangle is  {{{50/10=5*units}}}.


Each vertex angle of one isosceles triangle is  {{{360/10=36*degrees}}} and is a central angle of the circle.


Each base angle of one such isosceles triangle is  {{{(180-36)/2=72*degrees}}}.


Can you now continue with that to answer your questions?