a)
[tex](2sin60 - tg45)-8sin30 = (2*\frac{\sqrt{3}}{2} - 1)-8*\frac{1}{2} = (\sqrt{3} - 1) - 4 = \sqrt{3} -5[/tex]
b)
[tex]\alpha < 90\\tg\alpha = \frac{2}{3}\\tg\alpha = \frac{sin\alpha}{cos\alpha}\\cos\alpha tg\alpha = sin\alpha\\\frac{2}{3}cos\alpha = sin\alpha\\cos\alpha - sin\alpha = cos\alpha - \frac{2}{3}cos\alpha = \frac{1}{3}cos\alpha[/tex]
