Answer:
Inscribed Equilateral Triangle
Explanations:
From the given diagram, you can see that an arc was inscribed at 6 points on the circumference of the circle. This means that the diagram that will fit in must be a regular polygon with 6 vertices.
A regular polygon with 6 vertices is a hexagon and the type of shape we can create within the hexagon inscribed are equilateral triangles as shown below:
This shape forms an inscribed equilateral triangle. The largest equilateral triangle will fit in the circle, with each vertex touching the circle.