Question

4. Does any of the following, drawn in a rectangular coordinate plane, represent a
function?
(a) A circle
(c) A rectangle
(b) A triangle
(d) A downward-sloping straight line​

Answer 1

Answer:

Circles, rectangles, triangles would fail vertical line test. So they are not functions. A downward sloping straight line is a function.

However by applying suitable restrictions, a circle can be made a function. The top/bottom portion of a circle is a function.