For functions, there is only many input values, but there can be only one output value, and there can be no identical x values. For this, x=3.2. If y= 2*3.2 - 1, then y=5.4.
Answer:
domain is all real number
The complete question in the attached figure
we know that
the triangle ACB is an isosceles triangle
AC=AB----------> equals to the radius
so
∡ACB=∡CBA
the angle ∡CAB is equals to 54° by central angle
so
180°=54°+2*∡CBA--------> ∡CBA=[180-54]/2-----> 63°
∡CBA=63°
∡DBC=∡CBA-----------> ∡DBC=63°
the answer is∡DBC=63°