Question Number 65239 by Tawa1 last updated on 26/Jul/19
Commented by mr W last updated on 26/Jul/19
$$\mathrm{9}\left({D}−\mathrm{9}\right)=\mathrm{15}^{\mathrm{2}} \\ $$$${D}=\frac{\mathrm{15}^{\mathrm{2}} }{\mathrm{9}}+\mathrm{9}=\mathrm{34} \\ $$
Commented by Tony Lin last updated on 26/Jul/19
Commented by Tawa1 last updated on 26/Jul/19
$$\mathrm{God}\:\mathrm{bless}\:\mathrm{you}\:\mathrm{sir} \\ $$
Commented by Tawa1 last updated on 26/Jul/19
$$\mathrm{How}\:\mathrm{is}\:\:\:\:\:\mathrm{9}\left(\mathrm{D}\:−\:\mathrm{9}\right)\:=\:\mathrm{15}^{\mathrm{2}} \:\:\mathrm{sir} \\ $$
Commented by Tawa1 last updated on 26/Jul/19
$$\mathrm{I}\:\mathrm{combine}\:\mathrm{sir}\:\mathrm{tony}\:\mathrm{diagram}\:\mathrm{and}\:\mathrm{sir}\:\mathrm{ajfour}\:\mathrm{solution}\:\mathrm{so}\:\mathrm{i}\:\mathrm{understand} \\ $$$$\mathrm{very}\:\mathrm{well} \\ $$
Commented by mr W last updated on 26/Jul/19
Commented by mr W last updated on 26/Jul/19
$${CD}={diameter}={D} \\ $$$${EB}=\mathrm{30}/\mathrm{2}=\mathrm{15} \\ $$$$\frac{{CE}}{{EB}}=\frac{{EB}}{{ED}} \\ $$$$\Rightarrow\frac{\mathrm{9}}{\mathrm{15}}=\frac{\mathrm{15}}{{D}−\mathrm{9}} \\ $$$$\Rightarrow\mathrm{9}\left({D}−\mathrm{9}\right)=\mathrm{15}^{\mathrm{2}} \\ $$
Commented by Tawa1 last updated on 26/Jul/19
$$\mathrm{Thanks}\:\mathrm{for}\:\mathrm{your}\:\mathrm{time}\:\mathrm{sir}.\:\mathrm{God}\:\mathrm{bless}\:\mathrm{you} \\ $$
Answered by ajfour last updated on 26/Jul/19
$$\left({r}−\mathrm{9}\right)^{\mathrm{2}} +\mathrm{15}^{\mathrm{2}} ={r}^{\mathrm{2}} \\ $$$$\Rightarrow\:\:\mathrm{18}{r}=\mathrm{225}+\mathrm{81} \\ $$$$\Rightarrow\:{r}=\frac{\mathrm{306}}{\mathrm{18}}=\mathrm{17}\:\:\:\Rightarrow\:{D}=\mathrm{34}{cm}. \\ $$
Commented by Tawa1 last updated on 26/Jul/19
$$\mathrm{God}\:\mathrm{bless}\:\mathrm{you}\:\mathrm{sir} \\ $$