12)
$A = 7 \cdot \tan 42^\circ \cdot \tan 48^\circ - \dfrac{4 \cdot \cos 35^\circ}{\sin 55^\circ} + \sin^2 11^\circ + \sin^2 79^\circ$
$A = 7 \cdot \tan 42^\circ \cdot \cot (90^\circ - 48^\circ) - \dfrac{4 \cdot \cos 35^\circ}{\cos (90^\circ - 55^\circ)} + \sin^2 11^\circ + \cos^2 (90^\circ - 79^\circ)$
$A = 7 \cdot \tan 42^\circ \cdot \cot 42^\circ - \dfrac{4 \cdot \cos 35^\circ}{\cos 35^\circ} + \sin^2 11^\circ + \cos^2 11^\circ$
$A = 7 \cdot 1 - 4 \cdot 1 + 1$
$A = 7 - 4 + 1$
$A = 4$
`13,`
$B = \sin^2 52^\circ + \sin^2 38^\circ - \tan 31^\circ + \cot 59^\circ - \dfrac{\cot 22^\circ}{\tan 68^\circ}$
$B = \sin^2 52^\circ + \cos^2 (90^\circ - 38^\circ) - \tan 31^\circ + \tan (90^\circ - 59^\circ) - \dfrac{\cot 22^\circ}{\cot (90^\circ - 68^\circ)}$
$B = \sin^2 52^\circ + \cos^2 52^\circ - \tan 31^\circ + \tan 31^\circ - \dfrac{\cot 22^\circ}{\cot 22^\circ}$
$B = 1 - 0 - 1$
$B = 0$