А) ...
sin^2 t - 2 sin t * cos^2 t = 1- sin 2t
1- sin 2t = 1- sin 2t
б) ...
<span>2 cos^2 t = 1+ cos^2 t - sin^2 t </span>
2 cos^2 t= sin^2 t +cos^2 t - cos^2 t - sin^2 (синусы сокращаются)
<span>2 cos^2 t = 2 cos^2 t</span>
3.sin²a+23+3.cos²a=3.sin²a+3.cos²a+23=
=3(sin²a+cos²a)+23=3.1+23=3+23=26