Question

Express the area of ∆ABD in terms of θ:

Answer 1

((1-cosθ)sinθ)/2

Answer 2

How???

Answer 3

1/OC = OD
cosθ=1/OC
OD=cosθ
BD=sinθ
the area of ABD (triangle only) is AD*BD/2
AD=1-OD=1-cosθ
so
[ABD]=((1-cosθ)sinθ)/2

Answer 4

Express the area of the shaded region in terms of θ.
Hint: If A is the area of the sector of a circle,
\[A = \frac{ r ^{2}\theta }{ 2 }\]
where r is the radius of the circle and θ is the central angle.