What is the length of a rectangle formed from the lateral surface of a cylinder?
a) h
b) 2 pie r
c) 2 pie r h
d) pie r squared

For this case the lateral area of the cylinder is given by:
 
 Where,
 R: radius of the base of the cylinder
 h: cylinder height
 The length of the rectangle is:
 
 Substituting values:
 
 Simplifying we have:
 
 
 B) 2 * pi * r

Equatorial triangle and obtuce angle