If 
aand
rb
r
represent the adjacent sides of a triangle then its area is given as
1 |
|
2 a
b
 
r
r By definition of the area of a triangle, we have from
Fig 10 26,
Area of triangle ABC = 1 AB CD 2
⋅
But AB
|
b|
=
r  (as given), and CD = |
|
ar sinθ