ПОМОГИТЕ РЕШИТЬ ПЖЛСТ, С ОБЪЯСНЕНИЕМ

1)
$\sin \alpha + \cos \alpha = \frac{4}{3}\\\\ (\sin \alpha + \cos \alpha)^{2} = \frac{16}{9}\\\\ \sin^2\alpha + 2\sin\alpha\cos\alpha + \cos^2\alpha = \frac{16}{9}\\\\ 1 + 2\sin\alpha\cos\alpha = \frac{16}{9}\\\\ 2\sin\alpha\cos\alpha = \frac{16}{9} - 1\\\\ 2\sin\alpha\cos\alpha = \frac{7}{9}\\\\ \sin\alpha\cos\alpha = \frac{7}{18}\\\\$
2)
$(\sin \alpha + \cos\alpha)^2 = \sin^2\alpha+\cos^2\alpha + 2\sin\alpha\cos\alpha = 1+2*\frac{1}{3} = 1+\frac{2}{3} = \frac{5}{3}\\\\ (\sin \alpha + \cos\alpha)^2 = \frac{5}{3}\\\\ \sin \alpha + \cos\alpha = \sqrt{\frac{5}{3}}$