7. Let $\mathrm { b } ^ { 1 } 0$ and for $\mathrm { j } = 0,1,2$, $\_\_\_\_$ n , let Sj be the area of the region bounded by the y -axis and the curve xmy $= \sin$ by, $\quad \pi / \mathrm { b } \leq \mathrm { y } \leq ( ( \mathrm { j } + 1 ) \pi ) / \mathrm { b }$.
Show that S0, S1, S2, $\_\_\_\_$ Sn are in geometric progression. Also, find their sum for $\mathrm { a } = - 1$ and $\mathrm { b } = \pi$.\\