I don't get how you set up the equation for this problem:

Points A and B are ends of a diameter of a circle and C is a point on the circumference. Which of the following statements about triangle ABC is/are true?

a)The area is largest when the triangle is isosceles.

b)The area is smallest when the triangle is isosceles.

c)The perimeter is largest when the triangle is isosceles.

d)The perimeter is smallest when the triangle is isosceles.

Thanks again for your time.