Question

40 за один ! ((корень2)-sina-cosa)/(sina-cosa)

Answer 1

$\frac{\sqrt2-sina-cosa}{sina-cosa}=\frac{\sqrt2-(sina+cosa)}{sina-cosa}=\\\\\\\star \; sina+cosa=sina+sin(\frac{\pi}{2}-a)=2\, sin\frac{\pi}{4}\cdot cos(a-\frac{\pi}{4})=\sqrt2\, cos(x-\frac{\pi }{4})\; \star \\\\\star \; sina-cosa=sina-sin(\frac{\pi}{2}-a)=2sin(a-\frac{\pi}{4})\cdot cos\frac{\pi}{4}=\sqrt2\, sin(a-\frac{\pi}{4})\; \star \\\\\\=\frac{\sqrt2-\sqrt2\, sin(a-\frac{\pi}{4})}{\sqrt2\, cos(a-\frac{\pi}{4})}=\frac{1-sin(a-\frac{\pi}{4})}{cos(a-\frac{\pi}{4})}=\frac{1}{cos(a-\frac{\pi}{4})}-\frac{sin(a-\frac{\pi}{4})}{cos(a-\frac{\pi}{4})}=\\\\=\frac{1}{cos(a-\frac{\pi}{4})}-tg(a-\frac{\pi}{4})=sec(a-\frac{\pi}{4})-tg(a-\frac{\pi}{4})\; ;\\\\\star \; \; \frac{1}{cosx}=secx\; \; \star \\\\\\P.S.\\\\\star \; sin(a-\frac{\pi}{4})=cos(\frac{\pi}{2}-(a-\frac{\pi}{4}))= cos(\frac{\pi}{2}+\frac{\pi}{4}-a)=cos(\frac{3\pi}{4}-a)\; \star \\\\\frac{1-sin(a-\frac{\pi}{4})}{cos(a-\frac{\pi}{4})}=\frac{1-cos(\frac{3\pi}{4}-a)}{cos(a-\frac{\pi}{4})}=\frac{2sin^2(\frac{3\pi}{8}-\frac{a}{2})}{cos(a-\frac{\pi}{4})}$