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Mathematics

Find the values of

(i) 1cos230°1sin230°\sqrt{\dfrac{1 - \text{cos}^2 30°}{1 - \text{sin}^2 30°}}

(ii) sin 45° cos 45° cos 60°sin 60° cos 30° tan 45°\dfrac{\text{sin 45° cos 45° cos 60°}}{\text{sin 60° cos 30° tan 45°}}

Trigonometrical Ratios

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Answer

(i) Solving,

1cos230°1sin230°1(32)21(12)213411414341×43×413.\Rightarrow \sqrt{\dfrac{1 - \text{cos}^2 30°}{1 - \text{sin}^2 30°}} \\[1em] \Rightarrow \sqrt{\dfrac{1 - \Big(\dfrac{\sqrt{3}}{2}\Big)^2}{1 - \Big(\dfrac{1}{2}\Big)^2}} \\[1em] \Rightarrow \sqrt{\dfrac{1 - \dfrac{3}{4}}{1 - \dfrac{1}{4}}} \\[1em] \Rightarrow \sqrt{\dfrac{\dfrac{1}{4}}{\dfrac{3}{4}}} \\[1em] \Rightarrow \sqrt{\dfrac{1 \times 4}{3 \times 4}} \\[1em] \Rightarrow \dfrac{1}{\sqrt{3}}.

Hence, 1cos230°1sin230°=13\sqrt{\dfrac{1 - \text{cos}^2 30°}{1 - \text{sin}^2 30°}} = \dfrac{1}{\sqrt{3}}.

(ii) Solving,

sin 45° cos 45° cos 60°sin 60° cos 30° tan 45°12×12×1232×32×1143413.\Rightarrow \dfrac{\text{sin 45° cos 45° cos 60°}}{\text{sin 60° cos 30° tan 45°}} \\[1em] \Rightarrow \dfrac{\dfrac{1}{\sqrt{2}} \times \dfrac{1}{\sqrt{2}} \times \dfrac{1}{2}}{\dfrac{\sqrt{3}}{2} \times \dfrac{\sqrt{3}}{2} \times 1} \\[1em] \Rightarrow \dfrac{\dfrac{1}{4}}{\dfrac{3}{4}} \\[1em] \Rightarrow \dfrac{1}{3}.

Hence, sin 45° cos 45° cos 60°sin 60° cos 30° tan 45°=13.\dfrac{\text{sin 45° cos 45° cos 60°}}{\text{sin 60° cos 30° tan 45°}} = \dfrac{1}{3}.

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