Question
$\tan 105^{\circ}$ का मान ज्ञात कीजिए।

Answer

$\tan 105^{\circ}=\tan \left(60^{\circ}+45^{\circ}\right)=\frac{\tan 60^{\circ}+\tan 45^{\circ}}{1-\tan 60^{\circ} \tan 45^{\circ}}$
$\tan 105^{\circ}=\frac{\sqrt{3}+1}{1-\sqrt{3} \times 1}=\frac{\sqrt{3}+1}{1-\sqrt{3}}$
$\tan 105^{\circ}=\frac{\sqrt{3}+1}{1-\sqrt{3}} \times \frac{\sqrt{3}+1}{\sqrt{3}+1}=\frac{(\sqrt{3}+1)^2}{1-3}$
$=\frac{(\sqrt{3})^2+2 \times \sqrt{3}+(1)^2}{-2}$
$=\frac{3+2 \sqrt{3}+1}{-2}=\frac{4+2 \sqrt{3}}{-2}$
$=\frac{2(2+\sqrt{3})}{-2}=-(2+\sqrt{3})$

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