Refer to the figure, in which a unit circle is drawn. The line segment DR is tangent to the circle and 0 is acute 

(a) Express the area of ΔOBC in terms of sin θ and cos θ. 

(b) Express the area of ΔOBD in terms of sin θ and cos θ.

(c) The area of the sector O͡B͡C͡ of the circle is 1/2 θ where θ is measured in radians. Use the results of parts (a) and (b) and the fact that

to show that

Area AOBC < Area BC < Area AOBD sin 0 cos 0