A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 11cm + 13cm + 12cm = 36cm

The area of a parallelogram is equal to its length x width:

a = l x w
a = a x b
a = 5 x 8
a = 40

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).

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

sa = 2πr² + 2πrh
sa = 2π(2²) + 2π(2 x 7)
sa = 2π(4) + 2π(14)
sa = (2 x 4)π + (2 x 14)π
sa = 8π + 28π
sa = 36π