1.
[tex]a = 6 \ cm\\b = 8 \ cm\\\alpha = 45^{o}\\sin45^{o} = \frac{\sqrt{2}}{2}\\\\P = a\cdot b\cdot sin\alpha\\\\P = 6 \ cm\cdot 8 \ cm\cdot sin45^{o}\\\\P = 48 \ cm^{2}\cdot\frac{\sqrt{2}}{2}\\\\\boxed{P = 24\sqrt{2} \ cm^{2}}}[/tex]
2.
[tex]P=(-3, 7) \ \ \rightarrow \ \ x = -3, \ y = 7\\\\r^{2} = x^{2}+y^{2}\\\\r^{2}=(-3)^{2}+7^{2}\\\\r^{2} = 9+49\\\\r^{2} = 58\\\\r = \sqrt{58}\\\\\\cos \alpha = \frac{x}{y}\\\\cos\alpha = \frac{-3}{\sqrt{58}}\\\\\boxed{cos \alpha = -\frac{3\sqrt{58}}{58}}[/tex]
