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

p = x + y + z
p = 10cm + 10cm + 15cm = 35cm

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 40° - 23° = 117°

So, d° = 23° + 117° = 140°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 40° = 140°

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.

A line segment is a portion of a line with a measurable length. The midpoint of a line segment is the point exactly halfway between the endpoints. The midpoint bisects (cuts in half) the line segment.

The volume of a cylinder is πr²h:

v = πr²h
v = π(1² x 1)
v = 1π