24б
(tga+tgb)/tg(a+b)+(tga-tgb)/tg(a-b)=
=(tga+tgb):(tga+tgb)/(1-tgatgb)+(tga-tgb):(tga-tgb)/(1+tgatgb)=
=(tga+tgb)*(1-tgatgb)/(tga+tgb)+(tga-tgb)*(1+tgatgb)/(tga-tgb)=
=1-tgatgb+1+tgatgb=2
25a
(sin²t+2sintcost-cos²t)²=(-cos2t+sin2t)²=
=cos²2t-2cos2tsin2t+sin²2t=1-sin4t