11.2 Surface Area of Prisms and Cylinders

Prism - a polyhedron with exactly 2 congruent, parallel faces, called bases. (base shape names the prism)

Lateral faces - faces other than bases. In right prisms, these are rectangles.

Altitude - a segment in a prism that is perpendicular to bases

Height - the length of an altitude in a prism

Right prisms - lateral faces perpendicular to bases

Oblique prisms - lateral faces not perpendicular to bases.

bases triangular prism(right)

lateral edge

lateral face (rectangle)

oblique prism

Surface Area = lateral area + base area

Th. 11.1 Lateral and Surface Areas of a Prism

lateral area = ph (perimeter of base)(height of prism)

S.A. = L.A. + 2B

Ex 1: Find SA of rt. triangular prism: height 10 cm, base perimeter 18 cm, bases are equilateral triangles.

10

6

6

Base area =

Lateral area = ph

= 18 (10) = 180

S.A. = 2B + L.A. S.A. =

Cylinder 2 circles

1 rectangle

h

(r2 )

(circumference height)

Th. 11.2 Lateral and Surface Areas of a Cylinder

S.A. 2rh 2r2

(S.A. = L.A. + 2B)

Ex 2: Radius of cylinder base is 6 ft. and its height is 9 ft. Find S.A. in terms of .

S.A. 2rh 2r2

S.A. 2 (6)(9) 2 (6)2

S.A. 108 72

S.A. 180 ft 2

6

9