Question Number 3417 by RasheedSindhi last updated on 13/Dec/15
$${prove}\:{that}\:{among}\:{all}\:{closed}\:{figures} \\ $$$${having}\:{same}\:{perimeter}\:{circle} \\ $$$${has}\:{maximum}\:{area}. \\ $$
Commented by Filup last updated on 13/Dec/15
$$\mathrm{I}\:\mathrm{dont}\:\mathrm{understand}\:\mathrm{the}\:\mathrm{question} \\ $$
Commented by RasheedSindhi last updated on 13/Dec/15
$${Consider}\:{closed}\:{figures}\:{triangle}, \\ $$$${quadilateral},{pentagon}…{or}\:{other} \\ $$$${closed}\:{curves}\:{or}\:{mixture}\:{of}\:{curves} \\ $$$${and}\:{straight}\:{line}\:{segments}\:,{all} \\ $$$${having}\:{same}\:{perimeter}.{Among} \\ $$$${all}\:{the}\:{areas}\:{these}\:{figures}\:{have} \\ $$$${the}\:{largest}\:{is}\:{the}\:{area}\:{of}\:{circle}. \\ $$
Commented by 123456 last updated on 13/Dec/15
$$\mathrm{this}\:\mathrm{is}\:\mathrm{isoperemtric}\:\mathrm{inequality} \\ $$$$\mathrm{4}\pi\mathrm{A}\leqslant\mathrm{L}^{\mathrm{2}} \\ $$
Commented by Filup last updated on 13/Dec/15
$$\mathrm{Circle}\:\mathrm{is}\:\mathrm{essentially}\:\mathrm{an}\:\infty−{sided} \\ $$$${polygon} \\ $$
Commented by Filup last updated on 13/Dec/15
$$\mathrm{3}−\mathrm{gon}\:\left(\mathrm{triangle}\right)<\mathrm{4}−\mathrm{gon}\:\left(\mathrm{square}\right) \\ $$$$\mathrm{4}−\mathrm{gon}<\mathrm{5}−\mathrm{gon} \\ $$$$\mathrm{etc} \\ $$$$\therefore{n}−{gon}<\infty−{gon}\:\left({circle}\right) \\ $$
Commented by Rasheed Soomro last updated on 13/Dec/15
$$\mathcal{W}{hat}\:{is}\:{meant}\:{by}\:\mathrm{isoperemtric}\:\mathrm{inequality}\:? \\ $$
Commented by RasheedSindhi last updated on 13/Dec/15
$$\mathcal{T}{h}\propto{nk}\mathcal{S} \\ $$
Commented by prakash jain last updated on 13/Dec/15
$$\mathrm{isoperimetric}\:\mathrm{inequality}\:\mathrm{for}\:\mathrm{all}\:\mathrm{closed} \\ $$$$\mathrm{plane}\:\mathrm{figure} \\ $$$$\mathrm{4}\pi\mathrm{A}\leqslant\mathrm{L}^{\mathrm{2}} \\ $$$$\mathrm{A}\:\mathrm{area} \\ $$$$\mathrm{L}\:\mathrm{perimeter} \\ $$$$\mathrm{equality}\:\mathrm{holding}\:\mathrm{true}\:\mathrm{only}\:\mathrm{for}\:\mathrm{circle}. \\ $$