Parabola of the form y=x²: Write a function that expresses..

A circle has a radius of a.

Choose the function that expresses its circumference.

$y=2\pi a$

A circle has a radius a.

Choose the function that expresses the area of the circle.

$y=\pi a^2$

A square has a side length of a.

Which function expresses the area of the square?

$y=a^2$

A square has a side length of a.

Choose the function that expresses the perimeter of the square.

$y=4a$

A square has a side length of a.

Choose the function that expresses the area of the shaded triangle.

$y=\frac{a^2}{2}$

A square has sides measuring a.

Choose the function that expresses the length of the square's diagonal.

$y=\sqrt{2}a$