Question

надо упростить выражение

Answer 1

$\frac{sin^2 \phi-1}{cos^2\phi-1 }+ctg \phi*tg \phi = \frac{-cos^2 \phi}{-sin^2 \phi} +1=ctg^2 \phi+1 = \frac{1}{sin^2\phi }\\\\ \frac{tg^5a*cos^3a}{1+tg^2a}= \frac{sin^5a*cos^3a}{cos^5a* \frac{1}{cos^2a} }= \frac{sin^5a*cos^3a*cos^2a}{cos^5a} = \frac{sin^5a*cos^5a}{cos^5a}=sin^5a \\\\(sinx+1)(sinx-1)=sin^2a-1=-cos^2a$