Showing posts with label Triangular Pyramid. Show all posts
Showing posts with label Triangular Pyramid. Show all posts

Saturday, September 1, 2012

Triangular Pyramid How many Faces

Introduction

Triangular pyramid how many faces a pyramid is a solid three dimensional shape formed by  connecting the base which can be any polygon and the apex . Pyramids have a base which is a polygon with ' n ' sides then the number of faces it has will be equal to ' n '. If the number of faces is ' n ' then the number of vertices will be ' n + 1 '  and the number of edges are  ' 2n ' . Pyramids are specified according to their base shape , if it is unspecified then it is normally assumed the pyramid has a square base .

Triangular pyramid means it has a triangle base , when a pyramid is made up of four equilateral triangles then it is called a tetrahedron . A tetrahedron has four equilateral triangular faces (any one of the face can be considered as a base) , four vertices's and six edges . In a tetrahedron all angles and all edges are equal .



Triangular Pyramid How many Faces : Surface Area and Volume.

Triangular pyramid how many faces? A triangular pyramid has 3 faces  and one base , we can say it has all together 4 faces as we see a Tetrahedron has 4 faces each one is an equilateral triangle so any face may be considered as the base .

Surface Area
The surface area of a triangular pyramid is given by...

S.A = Area of base + 3 ( Area of a face ) = 1/2 s a + 3 ( 1/2 s l )

S.A  =  1/2 x s a + 3/2 s l  sq.units.   where ' a ' is the height of base triangle , ' s ' is the side length of the base triangle which is again the base of the face triangle , ' l ' is the slant height or the height of the face triangle .

For a tetrahedron surface area  S.A  =  4 ( 1/2 s a )  =  2 s a  ,  where ' s ' is the base of any face and ' a ' is the height or slant height .

Volume

Volume of a triangular pyramid is given by...

V  =  1/3 times Area of base triangle times height of the pyramid .

V =  1/3 x ( 1/2 s a ) h   =   1/6 s a h    cubic units

Triangular Pyramid How many Faces:example Problems

Ex 1:  Find the surface area and volume of the given triangular pyramid .

Sol :   Surface area  S.A  =  area of base + area of three faces            ( s = 6 cm , a = 4 cm , l = 8 cm  , h = 5 cm )

area of base  = 1/2 sa  =  1/2 x 6 x 4  = 12 cm2,  area of three faces  = 3/2 (sl) =   3/2 ( 6 x 8 )  =  3 ( 24 )  =  72 cm2

Therefore S.A  =  12 cm   +  72 cm      =   842 cm

Volume  V  =  1/6 sah    =   1/6 x 6 x 4 x 5  =  20 cm3

Ex 2 : The surface area of a tetrahedron is 112 m2 , find the area of the base.

Sol: A tetrahedron has four congruent faces , the area of  all four faces are equal and any face can be considered as base.

So , The area of the base in the given tetrahedron  =  112/4  =  28 m2   .

Algebra is widely used in day to day activities watch out for my forthcoming posts on polynomials and factoring and factoring polynomials degree 3. I am sure they will be helpful.