What is the formula to find a semicircle?

Answer 1

I think that you are asking for the equation of a semi-circle.

If you have a circle with radius r and centered at (0,0), its equation is x^2 + y^2 = r^2

The upper semicircle has the equation: y = sqrt(r^2 - x^2) with -r ≤ x ≤ r <------------------ Answer

By using the square root I only get points where the y coordinate is positive and thus all points are restricted to the upper semicircle.

The area is ((π * r^2) / 2)

The perimeter is (π * r)