The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(1²) + 2π(1 x 8)
sa = 2π(1) + 2π(8)
sa = (2 x 1)π + (2 x 8)π
sa = 2π + 16π
sa = 18π

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

To find the diagonal we need to know the length of one of the square's sides. We know the area and the area of a square is the length of one side squared:

a = s²

so the length of one side of the square is:

s = \( \sqrt{a} \) = \( \sqrt{25} \) = 5

The Pythagorean theorem defines the square of the hypotenuse (diagonal) of a triangle with a right angle as the sum of the squares of the other two sides:

c² = a² + b²
c² = 5² + 5²
c² = 50
c = \( \sqrt{50} \) = \( \sqrt{25 x 2} \) = \( \sqrt{25} \) \( \sqrt{2} \)
c = 5\( \sqrt{2} \)

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

a² - 9 = 0
(a - 3)(a + 3) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 3) or (a + 3) must equal zero:

If (a - 3) = 0, a must equal 3
If (a + 3) = 0, a must equal -3

So the solution is that a = 3 or -3

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 58° - 27° = 95°