Question Number 74726 by ajfour last updated on 29/Nov/19
Commented by ajfour last updated on 29/Nov/19
$${Find}\:{the}\:{sides}\:{of}\:{the}\:{squares}, \\ $$$${p},\:{q},\:{r}\:\:{in}\:{terms}\:{of}\:{a},\:{b},\:{c}\:. \\ $$
Commented by mr W last updated on 29/Nov/19
$${p}=\sqrt{\frac{\mathrm{2}\left({b}^{\mathrm{2}} +{c}^{\mathrm{2}} \right)−{a}^{\mathrm{2}} }{\mathrm{3}}} \\ $$$${q}=\sqrt{\frac{\mathrm{2}\left({c}^{\mathrm{2}} +{a}^{\mathrm{2}} \right)−{b}^{\mathrm{2}} }{\mathrm{3}}} \\ $$$${r}=\sqrt{\frac{\mathrm{2}\left({a}^{\mathrm{2}} +{b}^{\mathrm{2}} \right)−{c}^{\mathrm{2}} }{\mathrm{3}}} \\ $$
Commented by ajfour last updated on 29/Nov/19
$${Great},\:{Sir},\:{please}\:{explain},\:{i} \\ $$$${dont}\:{see}\:{a}\:\:{short}\:{way}.. \\ $$
Answered by mr W last updated on 29/Nov/19
$${let}'{s}\:{say}\:{p},\:{q},\:{r}\:{are}\:{sides}\:{of}\:{triangle}\:{ABC}.\: \\ $$$${p}^{\mathrm{2}} ={q}^{\mathrm{2}} +{r}^{\mathrm{2}} −\mathrm{2}{qr}\:\mathrm{cos}\:{A}\:\:\:…\left({I}\right) \\ $$$${we}\:{have}\:{also} \\ $$$${a}^{\mathrm{2}} ={q}^{\mathrm{2}} +{r}^{\mathrm{2}} −\mathrm{2}{qr}\:\mathrm{cos}\:\left(\pi−{A}\right)={q}^{\mathrm{2}} +{r}^{\mathrm{2}} +\mathrm{2}{qr}\:\mathrm{cos}\:{A}\:\:\:…\left({II}\right) \\ $$$$\left({I}\right)+\left({II}\right): \\ $$$$\Rightarrow{p}^{\mathrm{2}} +{a}^{\mathrm{2}} =\mathrm{2}\left({q}^{\mathrm{2}} +{r}^{\mathrm{2}} \right)\:\:\:…\left({i}\right) \\ $$$${similarly} \\ $$$$\Rightarrow{q}^{\mathrm{2}} +{b}^{\mathrm{2}} =\mathrm{2}\left({r}^{\mathrm{2}} +{p}^{\mathrm{2}} \right)\:\:\:…\left({ii}\right) \\ $$$$\Rightarrow{r}^{\mathrm{2}} +{c}^{\mathrm{2}} =\mathrm{2}\left({p}^{\mathrm{2}} +{q}^{\mathrm{2}} \right)\:\:\:…\left({iii}\right) \\ $$$$\left({i}\right)+\left({ii}\right)+\left({iii}\right): \\ $$$${a}^{\mathrm{2}} +{b}^{\mathrm{2}} +{c}^{\mathrm{2}} +\left({p}^{\mathrm{2}} +{q}^{\mathrm{2}} +{r}^{\mathrm{2}} \right)=\mathrm{4}\left({p}^{\mathrm{2}} +{q}^{\mathrm{2}} +{r}^{\mathrm{2}} \right) \\ $$$$\Rightarrow{p}^{\mathrm{2}} +{q}^{\mathrm{2}} +{r}^{\mathrm{2}} =\frac{{a}^{\mathrm{2}} +{b}^{\mathrm{2}} +{c}^{\mathrm{2}} }{\mathrm{3}}\:\:\:\:…\left({iv}\right) \\ $$$${put}\:\left({iv}\right)\:{into}\:\left({i}\right): \\ $$$$\Rightarrow{p}^{\mathrm{2}} +{a}^{\mathrm{2}} =\mathrm{2}\left(\frac{{a}^{\mathrm{2}} +{b}^{\mathrm{2}} +{c}^{\mathrm{2}} }{\mathrm{3}}−{p}^{\mathrm{2}} \right) \\ $$$$\Rightarrow{p}=\sqrt{\frac{\mathrm{2}\left({b}^{\mathrm{2}} +{c}^{\mathrm{2}} \right)−{a}^{\mathrm{2}} }{\mathrm{3}}} \\ $$$${similarly} \\ $$$$\Rightarrow{q}=\sqrt{\frac{\mathrm{2}\left({c}^{\mathrm{2}} +{a}^{\mathrm{2}} \right)−{b}^{\mathrm{2}} }{\mathrm{3}}} \\ $$$$\Rightarrow{r}=\sqrt{\frac{\mathrm{2}\left({a}^{\mathrm{2}} +{b}^{\mathrm{2}} \right)−{c}^{\mathrm{2}} }{\mathrm{3}}} \\ $$
Commented by ajfour last updated on 29/Nov/19
$${Wonderful},\:{Sir}.\:{I}\:{could}\:{have} \\ $$$${solved}\:{it}\:{had}\:{i}\:{proceeded}, \\ $$$${you}\:{put}\:{it}\:{in}\:{nice}\:{details},\:{sir}. \\ $$$${Thanks}. \\ $$
Commented by mr W last updated on 30/Nov/19
$${i}'{m}\:{sure}\:{you}\:{would}\:{come}\:{to}\:{the}\:{same} \\ $$$${solution}\:{sir}. \\ $$$${inspired}\:{by}\:{this}\:{question}\:{i}\:{have}\:{created} \\ $$$${a}\:{new}\:{question}\:{about}\:{the}\:{areas}\:{of}\:{the} \\ $$$${squares}.\:{please}\:{give}\:{a}\:{try}\:{sir}. \\ $$