Question

Help me pleas algebra .

Answer 1

а)
$1-sin^2 \alpha +ctg^2 \alpha *sin^2 \alpha=cos^2 \alpha + \frac{cos^2 \alpha *sin^2 \alpha }{sin^2 \alpha} =2cos^2 \alpha$
б)
$(tg \alpha *cos \alpha )^2+(ctg \alpha *sin \alpha )^2=sin^2 \alpha +cos^2 \alpha =1$