Do you know the formula for the area of a whole circle?

Use that to find the correct radius for this circular design.

There are three equal "tears", what angle of rotation do you need for one "tear" to match with its neighbour?

What angle do you have in an equilateral triangle?

How does that help with the angle you need to make at the centre?

Three semicircles arc from the edge to the centre of the design.

Where is the centre for each semi-circular arc, and how will you locate each point accurately?