A manometer has a vertical arm of cross sectional area 9A and an inclined arm having area of cross section A. The density of the manometer liquid has a specific gravity of 0.74. the scale attached to the inclined arm can read up to `+-0.5mm`. It is desired that the manometer shall record pressure difference `(P_(1)-P_(2))` up to an accuracy of `+- 0.09` mm of water. To acheive this, what should be the inclination angle `theta` of the inclined arm.

Answer

`theta=sin^(-1)(0.13)`