Question

а) (1-cos a) (1 + cos a) (1+ ctg² a). б) _(sin + cos a)² + 2sin a cos a

Answer 1

a) (1-cos^2a)(1+ctg^2a)=sin^2a×1/sin^2a=1
б) -(sin^2a+cos^2a+2sin a cos a)+2sin a cos a= -sin^2a-cos^2a=-(sin^2a+cos^2a)=-1