$ \tan 6^\circ + \tan 42^\circ + \tan 66^\circ + \tan 78^\circ = $

The maximum value of $12\sin x - 5\cos x + 3$ is

$\sin^2 16^\circ - \sin^2 76^\circ = $

By considering $1^{\prime}=0.0175$, he approximate value of $\cot 45^{\circ} 2^{\prime}$ is