Question

1. (1+ctg^2a)*sin^2a+1
2. (tga*ctga-cos^2a)*1/sin^2a
3. tga*ctga+sina

Answer 1

1.(1+ctg^2a)*sin^2a+1=1/sin^2a*sin^2a+1=1+1=2
2. (tga*ctga-cos^2a)*1/sin^2a=(1-cos^2a)*1/sin^2a=sin^2a*1/sin^2a=1
3.tga*ctga+sina=1+sina