Find the area of a quadrilateral ABCD is which AB = 3 cm, BC = 4 cm, CD = 4 cm, DA = 5 cm and AC = 5 cm.
Let consider a quadrilateral ABCD
In ∆ABC;
AB = a = 3 cm, BC = b = 4cm, AC = c = 5 cm
Let a, b and c are the sides of triangle and s is
the semi-perimeter, then its area is given by:
A = 
where 
[Heron’s Formula]
= 
= 6
A1 = 
A1 = 
= 
cm2
In ∆ADC;
DA = a = 5 cm, CD = 4 = 4cm, AC = c = 5 cm
Let a, b and c are the sides of triangle and s is
the semi-perimeter, then its area is given by:
A = 
where 
= 
= 7
A2 = 
A2 = 
= 
cm2
Therefore area of quadrilateral ABCD = A1 + A2 = 6+9.16 = 15.16 cm2
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