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Question Number 133996 by mr W last updated on 26/Feb/21
show that (√2)<log_2  3<(√3)
$${show}\:{that}\:\sqrt{\mathrm{2}}<\mathrm{log}_{\mathrm{2}} \:\mathrm{3}<\sqrt{\mathrm{3}} \\ $$
Answered by som(math1967) last updated on 26/Feb/21
  2^(√2) <3<2^(√3)   log_2 2^(√2) <log_2 3<log_2 2^(√3)   (√2)<log_2 3<(√3)
$$\:\:\mathrm{2}^{\sqrt{\mathrm{2}}} <\mathrm{3}<\mathrm{2}^{\sqrt{\mathrm{3}}} \\ $$$${log}_{\mathrm{2}} \mathrm{2}^{\sqrt{\mathrm{2}}} <{log}_{\mathrm{2}} \mathrm{3}<{log}_{\mathrm{2}} \mathrm{2}^{\sqrt{\mathrm{3}}} \\ $$$$\sqrt{\mathrm{2}}<{log}_{\mathrm{2}} \mathrm{3}<\sqrt{\mathrm{3}} \\ $$
Commented by som(math1967) last updated on 26/Feb/21
Is my way correct sir?
$${Is}\:{my}\:{way}\:{correct}\:{sir}? \\ $$
Commented by mr W last updated on 26/Feb/21
we may not use calculator. how is it  obviour that 2^(√2) <3<2^(√3)  ?
$${we}\:{may}\:{not}\:{use}\:{calculator}.\:{how}\:{is}\:{it} \\ $$$${obviour}\:{that}\:\mathrm{2}^{\sqrt{\mathrm{2}}} <\mathrm{3}<\mathrm{2}^{\sqrt{\mathrm{3}}} \:? \\ $$
Answered by mr W last updated on 26/Feb/21
9>8  3^2 >2^3   2 log_2  3>3  log_2  3>(3/2)  (log_2  3)^2 >((3/2))^2 =(9/4)>(8/4)=2  ⇒log_2  3>(√2)    27<32  3^3 <2^5   3log_2  3<5  log_2  3<(5/3)  (log_2  3)^2 <((5/3))^2 =((25)/9)<((27)/9)=3  ⇒log_2  3<(√3)
$$\mathrm{9}>\mathrm{8} \\ $$$$\mathrm{3}^{\mathrm{2}} >\mathrm{2}^{\mathrm{3}} \\ $$$$\mathrm{2}\:\mathrm{log}_{\mathrm{2}} \:\mathrm{3}>\mathrm{3} \\ $$$$\mathrm{log}_{\mathrm{2}} \:\mathrm{3}>\frac{\mathrm{3}}{\mathrm{2}} \\ $$$$\left(\mathrm{log}_{\mathrm{2}} \:\mathrm{3}\right)^{\mathrm{2}} >\left(\frac{\mathrm{3}}{\mathrm{2}}\right)^{\mathrm{2}} =\frac{\mathrm{9}}{\mathrm{4}}>\frac{\mathrm{8}}{\mathrm{4}}=\mathrm{2} \\ $$$$\Rightarrow\mathrm{log}_{\mathrm{2}} \:\mathrm{3}>\sqrt{\mathrm{2}} \\ $$$$ \\ $$$$\mathrm{27}<\mathrm{32} \\ $$$$\mathrm{3}^{\mathrm{3}} <\mathrm{2}^{\mathrm{5}} \\ $$$$\mathrm{3log}_{\mathrm{2}} \:\mathrm{3}<\mathrm{5} \\ $$$$\mathrm{log}_{\mathrm{2}} \:\mathrm{3}<\frac{\mathrm{5}}{\mathrm{3}} \\ $$$$\left(\mathrm{log}_{\mathrm{2}} \:\mathrm{3}\right)^{\mathrm{2}} <\left(\frac{\mathrm{5}}{\mathrm{3}}\right)^{\mathrm{2}} =\frac{\mathrm{25}}{\mathrm{9}}<\frac{\mathrm{27}}{\mathrm{9}}=\mathrm{3} \\ $$$$\Rightarrow\mathrm{log}_{\mathrm{2}} \:\mathrm{3}<\sqrt{\mathrm{3}} \\ $$
Commented by som(math1967) last updated on 27/Feb/21
ok sir
$${ok}\:{sir} \\ $$

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