Write a function named triangleArea which takes either one, two or three positive floats as parameters . If three parameters a, b and c are provided, the function should return the area of a triangle with side lenghts a,b,c. If two parameters a and b are provided it should return the area of a isosceles triangle with side lenghts a, a and b. If a single parameter "a" is provided then the function should return the area of a equilateral triangle with side lenghts a, a, a. (python)