Question

кто знает как решить?​

Answer 1

$1)\frac{Cos2\beta+Cos4\beta}{Cos\beta}=\frac{2Cos\frac{2\beta+4\beta}{2}*Cos\frac{2\beta-4\beta}{2}}{Cos\beta}=\frac{2Cos3\beta*Cos\beta}{Cos\beta}=2Cos3\beta\\\\2)\frac{2Cos\alpha}{2Sin\alpha}=\frac{2Cos\alpha}{2Sin\alpha Cos\alpha}=\frac{1}{Sin\alpha}$

$3)\frac{1}{Cos^{2}\alpha} -Cos^{2}\beta-Sin^{2} \beta= \frac{1}{Cos^{2}\alpha} -(Cos^{2}\beta+Sin^{2}\beta)=\frac{1}{Cos^{2}\alpha}-1=\frac{1-Cos^{2}\alpha}{Cos^{2}\alpha}=\frac{Sin^{2}\alpha}{Cos^{2}\alpha}=tg^{2}\alpha$

$4)CosyCos5y+SinySin5y=Cos(y-5y)=Cos(-4y)=Cos4y$