2
⋅
But AB
|
b|
=
r  (as given), and CD = |
|
ar sinθ Thus,  Area of triangle ABC = 1 |
||
| sin
2 b
a
θ
r
r
 
1 |
| 2 a
b
=
×
r
r
9 If 
a  and  
rb
r
 represent the adjacent sides of a  parallelogram, then its area is
given by |
|
a
b
×
r
r