Problem

\Delta PQR

is a triangle of area

\Delta

with

a = 2, b = \frac{7}{2}

and

c = \frac{5}{2}

, where

a, b

and

c

are the lengths of the sides of the triangle opposite to the angles at

P, Q

and

R

, respectively. Then,

\frac{2 \sin P - \sin 2P}{2 \sin P + \sin 2P}

equals a.

\frac{3}{4\Delta}

\frac{45}{4\Delta}

\left(\frac{3}{4\Delta}\right)^2

\left(\frac{45}{4\Delta}\right)^5