A) \[5\pi \,c{{m}^{2}}\]
B) \[10\pi \,c{{m}^{2}}\]
C) \[15\pi \,c{{m}^{2}}\]
D) \[40\pi \,c{{m}^{2}}\]
Correct Answer: B
Solution :
Equation of circle is,\[{{x}^{2}}+{{y}^{2}}={{5}^{2}}\] \[\therefore \,\,{{y}^{2}}=25-{{x}^{2}}\], \[2y\frac{dy}{dx}=-2x\], \[\therefore \frac{dy}{dx}=-\frac{x}{y}\] Curved surface of frustum \[=2\pi \int_{2}^{3}{yds}\]\[=2\pi \int_{2}^{3}{y.\frac{5}{y}dx}\] \[=2\pi \int_{2}^{3}{5dx}\]\[=2\pi [5x]_{2}^{3}=10\pi \,c{{m}^{2}}\].You need to login to perform this action.
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