Question
Evaluate: $\tan 40^{\circ} \times \tan 50^{\circ}$
✓
Answer
$\tan 40^{\circ} \times \tan \left(90^{\circ}-40^{\circ}\right)$
$\Rightarrow \tan 40^{\circ} \times \cot 40^{\circ}$
$\Rightarrow \tan 40^{\circ} \times \frac{1}{\tan 40^{\circ}}$
$\Rightarrow 1$
$\Rightarrow \tan 40^{\circ} \times \cot 40^{\circ}$
$\Rightarrow \tan 40^{\circ} \times \frac{1}{\tan 40^{\circ}}$
$\Rightarrow 1$
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