A) 30
B) 12.5
C) 10
D) 25
Correct Answer: D
Solution :
Total length \[=r+r+r\theta =20\] \[\theta =\frac{20-2r}{r}\] \[Area=\frac{1}{2}{{r}^{2}}\theta =\frac{1}{2}{{r}^{2}}\left( \frac{20-2r}{r} \right)\] \[A=10r-{{r}^{2}}\] \[\frac{dA}{dr}=0\] \[10-2r=0,\,r=5\] \[A=50-25=25\]You need to login to perform this action.
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