Question Number 222025 by fantastic last updated on 15/Jun/25
![(((5cos^2 (π/3)+4sec^2 (π/6)−tan^2 (π/4))/(sin^2 (π/6)+cos^2 (π/6))))=?? [easy mode]](https://www.tinkutara.com/question/Q222025.png)
$$\left(\frac{\mathrm{5cos}\:^{\mathrm{2}} \frac{\pi}{\mathrm{3}}+\mathrm{4sec}\:^{\mathrm{2}} \frac{\pi}{\mathrm{6}}−\mathrm{tan}\:^{\mathrm{2}} \frac{\pi}{\mathrm{4}}}{\mathrm{sin}\:^{\mathrm{2}} \frac{\pi}{\mathrm{6}}+\mathrm{cos}\:^{\mathrm{2}} \frac{\pi}{\mathrm{6}}}\right)=?? \\ $$$$\left[{easy}\:{mode}\right] \\ $$
Answered by MrGaster last updated on 16/Jun/25

$$\mathrm{cos}\frac{\pi}{\mathrm{3}}=\frac{\mathrm{1}}{\mathrm{2}},\mathrm{cos}^{\mathrm{2}} \frac{\pi}{\mathrm{3}}=\left(\frac{\mathrm{1}}{\mathrm{2}}\right)^{\mathrm{2}} =\frac{\mathrm{1}}{\mathrm{4}} \\ $$$$\mathrm{cos}\frac{\pi}{\mathrm{6}}=\frac{\sqrt{\mathrm{3}}}{\mathrm{2}},\mathrm{sec}\frac{\pi}{\mathrm{6}}=\frac{\mathrm{1}}{\mathrm{cos}\frac{\pi}{\mathrm{6}}}=\frac{\mathrm{1}}{\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}}=\frac{\mathrm{2}}{\:\sqrt{\mathrm{3}}},\mathrm{sec}^{\mathrm{2}} \frac{\pi}{\mathrm{6}}=\left(\frac{\mathrm{2}}{\:\sqrt{\mathrm{3}}}\right)^{\mathrm{2}} =\frac{\mathrm{4}}{\mathrm{3}} \\ $$$$\mathrm{tan}\frac{\pi}{\mathrm{4}}=\mathrm{1},\mathrm{tan}^{\mathrm{2}} \frac{\pi}{\mathrm{4}}=\mathrm{1}^{\mathrm{2}} =\mathrm{1} \\ $$$$\mathrm{Molecule}: \\ $$$$\mathrm{5}\centerdot\mathrm{cos}^{\mathrm{2}} \frac{\pi}{\mathrm{3}}+\mathrm{4}\centerdot\mathrm{sec}^{\mathrm{2}} \frac{\pi}{\mathrm{6}}−\mathrm{tan}^{\mathrm{2}} \frac{\pi}{\mathrm{4}}=\mathrm{5}\centerdot\frac{\mathrm{1}}{\mathrm{4}}+\mathrm{4}\centerdot\frac{\mathrm{4}}{\mathrm{3}}−\mathrm{1}=\frac{\mathrm{5}}{\mathrm{4}}+\frac{\mathrm{16}}{\mathrm{3}}−\mathrm{1} \\ $$$$\mathrm{General}\:\mathrm{score}\:\left(\mathrm{denominator}\right. \\ $$$$\left.\mathrm{12}\right): \\ $$$$\frac{\mathrm{5}}{\mathrm{4}}=\frac{\mathrm{15}}{\mathrm{12}},\frac{\mathrm{16}}{\mathrm{3}}=\frac{\mathrm{64}}{\mathrm{12}},\mathrm{1}=\frac{\mathrm{12}}{\mathrm{12}} \\ $$$$\frac{\mathrm{15}}{\mathrm{12}}+\frac{\mathrm{64}}{\mathrm{12}}−\frac{\mathrm{12}}{\mathrm{12}}=\frac{\mathrm{15}+\mathrm{64}−\mathrm{12}}{\mathrm{12}}=\frac{\mathrm{67}}{\mathrm{12}} \\ $$$$\mathrm{Denominator}: \\ $$$$\mathrm{sin}^{\mathrm{2}} \frac{\pi}{\mathrm{6}}+\mathrm{cos}^{\mathrm{2}} \frac{\pi}{\mathrm{6}}=\left(\frac{\mathrm{1}}{\mathrm{2}}\right)^{\mathrm{2}} +\left(\frac{\sqrt{\mathrm{3}}}{\mathrm{2}}\right)^{\mathrm{2}} =\frac{\mathrm{1}}{\mathrm{4}}+\frac{\mathrm{3}}{\mathrm{4}}=\mathrm{1}\:\left(\because\forall\theta,\mathrm{sin}^{\mathrm{2}} \theta+\mathrm{cos}^{\mathrm{2}} \theta=\mathrm{1}\right) \\ $$$$\frac{\frac{\mathrm{67}}{\mathrm{12}}}{\mathrm{1}}=\frac{\mathrm{67}}{\mathrm{12}} \\ $$