a semicircle has a radius of 12 . what is the approximate perimeter of the semicircle ?
"the perimeter of a circle is 2 * pi * r . the perimeter of a semicircle is 2 * pi * r / 2 + 2 r = pi * r + 2 r the perimeter is pi * 12 + 2 * 12 which is about 62 . the answer is b ."
add(divide(circumface(12), const_2), multiply(const_2, 12))