Question

Please help me!!!! So confused

Answer 1

Question:

The area of the kite is 48 cm². What are the lengths of the diagonals PR and QS?

________


Solution:

You can split the kite into two isosceles triangles:   PSR and PQR.

Assume that both diagonals intersect each other at the point O.


•   Area of the triangle PSR:

           m(PR) · m(OS)
A₁  =  ————————
                     2

           (x + x) · x
A₁  =  ——————
                  2


           2x · x
A₁  =  ————
              2


A₁ = x²        (i)


•   Area of the triangle PQR:

            m(PR) · m(PQ)
A₂  =  ————————
                     2

           (x + x) · 2x
A₂  =  ——————
                  2

           2x · 2x
A₂  =  ————
               2

           4x²
A₂  =  ———
             2


A₂ = 2x²        (ii)


So the total area of the kite is

A = A₁ + A₂ = 48


Then,

x² + 2x² = 48

3x² = 48

            48
x²  =  ———
            3

x² = 16

x = √16

x = 4 cm


•   Length of the diagonal PR:

m(PR) = x + x

m(PR) = 2x

m(PR) = 2 · 4

m(PR) = 8 cm


•   Length of the diagonal SQ:

m(SQ) = x + 2x

m(SQ) = 3x

m(SQ) = 3 · 4

m(SQ) = 12 cm


I hope this helps. =)


Tags:  polygon area triangle plane geometry