Question

a) 1-sin^2a + ctg^2a * sin^2a

b) (tga * cosa)^2 + (ctga * sina)^2

Answer 1

$a)~~ 1-sin^2 alpha +ctg^2 alpha sin^2 alpha =cos^2 alpha +cos^2 alpha =2cos^2 alpha$

$b)~~ (tg alpha cos alpha )^2+(ctg alpha sin alpha )^2=sin^2 alpha +cos^2 alpha =1$